Headgear for a patient interface

ABSTRACT

A positioning and stabilising structure comprising at least one gas delivery tube to receive the flow of air from a connection port on top of the patient&#39;s head and to deliver the flow of air to the entrance of the patient&#39;s airways via the seal-forming structure, the at least one gas delivery tube comprising a tube wall having an extendable concertina structure comprising a plurality of folds in the tube wall alternatingly forming a plurality of ridges and a plurality of grooves, the folds able to be at least partially unfolded to increase a separation of the ridges to elongate the extendable concertina structure; and one or more ridge connecting portions provided to the tube wall, each of the one or more ridge connecting portions connecting two or more adjacent ridges of the plurality of ridges and being configured to resist the separation of the ridges.

1 CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/269,916, filed Feb. 19, 2021, now allowed, which is the U.S. nationalphase of International Application No. PCT/AU2019/050874 filed Aug. 20,2019 which designated the U.S. and claims priority to U.S. ProvisionalApplication No. 62/764,995, filed Aug. 20, 2018, the entire contents ofeach of which are hereby incorporated by reference.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in Patent Office patent files orrecords, but otherwise reserves all copyright rights whatsoever.

2 BACKGROUND OF THE TECHNOLOGY 2.1 Field of the Technology

The present technology relates to one or more of the screening,diagnosis, monitoring, treatment, prevention and amelioration ofrespiratory-related disorders. The present technology also relates tomedical devices or apparatus, and their use.

2.2 Description of the Related Art 2.2.1 Human Respiratory System andits Disorders

The respiratory system of the body facilitates gas exchange. The noseand mouth form the entrance to the airways of a patient.

The airways include a series of branching tubes, which become narrower,shorter and more numerous as they penetrate deeper into the lung. Theprime function of the lung is gas exchange, allowing oxygen to move fromthe inhaled air into the venous blood and carbon dioxide to move in theopposite direction. The trachea divides into right and left mainbronchi, which further divide eventually into terminal bronchioles. Thebronchi make up the conducting airways, and do not take part in gasexchange. Further divisions of the airways lead to the respiratorybronchioles, and eventually to the alveoli. The alveolated region of thelung is where the gas exchange takes place, and is referred to as therespiratory zone. See “Respiratory Physiology”, by John B. West,Lippincott Williams & Wilkins, 9th edition published 2012.

A range of respiratory disorders exist. Certain disorders may becharacterised by particular events, e.g. apneas, hypopneas, andhyperpneas.

Examples of respiratory disorders include Obstructive Sleep Apnea (OSA),Cheyne-Stokes Respiration (CSR), respiratory insufficiency, ObesityHyperventilation Syndrome (OHS), Chronic Obstructive Pulmonary Disease(COPD), Neuromuscular Disease (NMD) and Chest wall disorders.

Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing(SDB), is characterised by events including occlusion or obstruction ofthe upper air passage during sleep. It results from a combination of anabnormally small upper airway and the normal loss of muscle tone in theregion of the tongue, soft palate and posterior oropharyngeal wallduring sleep. The condition causes the affected patient to stopbreathing for periods typically of 30 to 120 seconds in duration,sometimes 200 to 300 times per night. It often causes excessive daytimesomnolence, and it may cause cardiovascular disease and brain damage.The syndrome is a common disorder, particularly in middle agedoverweight males, although a person affected may have no awareness ofthe problem. See U.S. Pat. No. 4,944,310 (Sullivan).

Cheyne-Stokes Respiration (CSR) is another form of sleep disorderedbreathing. CSR is a disorder of a patient's respiratory controller inwhich there are rhythmic alternating periods of waxing and waningventilation known as CSR cycles. CSR is characterised by repetitivede-oxygenation and re-oxygenation of the arterial blood. It is possiblethat CSR is harmful because of the repetitive hypoxia. In some patientsCSR is associated with repetitive arousal from sleep, which causessevere sleep disruption, increased sympathetic activity, and increasedafterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones).

Respiratory failure is an umbrella term for respiratory disorders inwhich the lungs are unable to inspire sufficient oxygen or exhalesufficient CO₂ to meet the patient's needs. Respiratory failure mayencompass some or all of the following disorders.

A patient with respiratory insufficiency (a form of respiratory failure)may experience abnormal shortness of breath on exercise.

Obesity Hyperventilation Syndrome (OHS) is defined as the combination ofsevere obesity and awake chronic hypercapnia, in the absence of otherknown causes for hypoventilation. Symptoms include dyspnea, morningheadache and excessive daytime sleepiness.

Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a groupof lower airway diseases that have certain characteristics in common.These include increased resistance to air movement, extended expiratoryphase of respiration, and loss of the normal elasticity of the lung.Examples of COPD are emphysema and chronic bronchitis. COPD is caused bychronic tobacco smoking (primary risk factor), occupational exposures,air pollution and genetic factors. Symptoms include: dyspnea onexertion, chronic cough and sputum production.

Neuromuscular Disease (NMD) is a broad term that encompasses manydiseases and ailments that impair the functioning of the muscles eitherdirectly via intrinsic muscle pathology, or indirectly via nervepathology. Some NMD patients are characterised by progressive muscularimpairment leading to loss of ambulation, being wheelchair-bound,swallowing difficulties, respiratory muscle weakness and, eventually,death from respiratory failure. Neuromuscular disorders can be dividedinto rapidly progressive and slowly progressive: (i) Rapidly progressivedisorders: Characterised by muscle impairment that worsens over monthsand results in death within a few years (e.g. Amyotrophic lateralsclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers);(ii) Variable or slowly progressive disorders: Characterised by muscleimpairment that worsens over years and only mildly reduces lifeexpectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic musculardystrophy). Symptoms of respiratory failure in NMD include: increasinggeneralised weakness, dysphagia, dyspnea on exertion and at rest,fatigue, sleepiness, morning headache, and difficulties withconcentration and mood changes.

Chest wall disorders are a group of thoracic deformities that result ininefficient coupling between the respiratory muscles and the thoraciccage. The disorders are usually characterised by a restrictive defectand share the potential of long term hypercapnic respiratory failure.Scoliosis and/or kyphoscoliosis may cause severe respiratory failure.Symptoms of respiratory failure include: dyspnea on exertion, peripheraloedema, orthopnea, repeated chest infections, morning headaches,fatigue, poor sleep quality and loss of appetite.

A range of therapies have been used to treat or ameliorate suchconditions. Furthermore, otherwise healthy individuals may takeadvantage of such therapies to prevent respiratory disorders fromarising. However, these have a number of shortcomings.

2.2.2 Therapy

Various therapies, such as Continuous Positive Airway Pressure (CPAP)therapy, Non-invasive ventilation (NIV) and Invasive ventilation (IV)have been used to treat one or more of the above respiratory disorders.

Continuous Positive Airway Pressure (CPAP) therapy has been used totreat Obstructive Sleep Apnea (OSA). The mechanism of action is thatcontinuous positive airway pressure acts as a pneumatic splint and mayprevent upper airway occlusion, such as by pushing the soft palate andtongue forward and away from the posterior oropharyngeal wall. Treatmentof OSA by CPAP therapy may be voluntary, and hence patients may electnot to comply with therapy if they find devices used to provide suchtherapy one or more of: uncomfortable, difficult to use, expensive andaesthetically unappealing.

Non-invasive ventilation (NIV) provides ventilatory support to a patientthrough the upper airways to assist the patient breathing and/ormaintain adequate oxygen levels in the body by doing some or all of thework of breathing. The ventilatory support is provided via anon-invasive patient interface. NIV has been used to treat CSR andrespiratory failure, in forms such as OHS, COPD, NMD and Chest Walldisorders. In some forms, the comfort and effectiveness of thesetherapies may be improved.

Invasive ventilation (IV) provides ventilatory support to patients thatare no longer able to effectively breathe themselves and may be providedusing a tracheostomy tube. In some forms, the comfort and effectivenessof these therapies may be improved.

2.2.3 Treatment Systems

These therapies may be provided by a treatment system or device. Suchsystems and devices may also be used to screen, diagnose, or monitor acondition without treating it.

A treatment system may comprise a Respiratory Pressure Therapy Device(RPT device), an air circuit, a humidifier, a patient interface, anddata management.

Another form of treatment system is a mandibular repositioning device.

2.2.3.1 Patient Interface

A patient interface may be used to interface respiratory equipment toits wearer, for example by providing a flow of air to an entrance to theairways. The flow of air may be provided via a mask to the nose and/ormouth, a tube to the mouth or a tracheostomy tube to the trachea of apatient. Depending upon the therapy to be applied, the patient interfacemay form a seal, e.g., with a region of the patient's face, tofacilitate the delivery of gas at a pressure at sufficient variance withambient pressure to effect therapy, e.g., at a positive pressure ofabout 10 cmH₂O relative to ambient pressure. For other forms of therapy,such as the delivery of oxygen, the patient interface may not include aseal sufficient to facilitate delivery to the airways of a supply of gasat a positive pressure of about 10 cmH₂O.

Certain other mask systems may be functionally unsuitable for thepresent field. For example, purely ornamental masks may be unable tomaintain a suitable pressure. Mask systems used for underwater swimmingor diving may be configured to guard against ingress of water from anexternal higher pressure, but not to maintain air internally at a higherpressure than ambient.

Certain masks may be clinically unfavourable for the present technologye.g. if they block airflow via the nose and only allow it via the mouth.

Certain masks may be uncomfortable or impractical for the presenttechnology if they require a patient to insert a portion of a maskstructure in their mouth to create and maintain a seal via their lips.

Certain masks may be impractical for use while sleeping, e.g. forsleeping while lying on one's side in bed with a head on a pillow.

The design of a patient interface presents a number of challenges. Theface has a complex three-dimensional shape. The size and shape of nosesand heads varies considerably between individuals. Since the headincludes bone, cartilage and soft tissue, different regions of the facerespond differently to mechanical forces. The jaw or mandible may moverelative to other bones of the skull. The whole head may move during thecourse of a period of respiratory therapy.

As a consequence of these challenges, some masks suffer from being oneor more of obtrusive, aesthetically undesirable, costly, poorly fitting,difficult to use, and uncomfortable especially when worn for longperiods of time or when a patient is unfamiliar with a system. Wronglysized masks can give rise to reduced compliance, reduced comfort andpoorer patient outcomes. Masks designed solely for aviators, masksdesigned as part of personal protection equipment (e.g. filter masks),SCUBA masks, or for the administration of anaesthetics may be tolerablefor their original application, but nevertheless such masks may beundesirably uncomfortable to be worn for extended periods of time, e.g.,several hours. This discomfort may lead to a reduction in patientcompliance with therapy. This is even more so if the mask is to be wornduring sleep.

CPAP therapy is highly effective to treat certain respiratory disorders,provided patients comply with therapy. If a mask is uncomfortable, ordifficult to use a patient may not comply with therapy. Since it isoften recommended that a patient regularly wash their mask, if a mask isdifficult to clean (e.g., difficult to assemble or disassemble),patients may not clean their mask and this may impact on patientcompliance.

While a mask for other applications (e.g. aviators) may not be suitablefor use in treating sleep disordered breathing, a mask designed for usein treating sleep disordered breathing may be suitable for otherapplications.

For these reasons, patient interfaces for delivery of CPAP during sleepform a distinct field.

2.2.3.1.1 Seal-Forming Structure

Patient interfaces may include a seal-forming structure. Since it is indirect contact with the patient's face, the shape and configuration ofthe seal-forming structure can have a direct impact the effectivenessand comfort of the patient interface.

A patient interface may be partly characterised according to the designintent of where the seal-forming structure is to engage with the face inuse. In one form of patient interface, a seal-forming structure maycomprise a first sub-portion to form a seal around the left naris and asecond sub-portion to form a seal around the right naris. In one form ofpatient interface, a seal-forming structure may comprise a singleelement that surrounds both nares in use. Such single element may bedesigned to for example overlay an upper lip region and a nasal bridgeregion of a face. In one form of patient interface a seal-formingstructure may comprise an element that surrounds a mouth region in use,e.g. by forming a seal on a lower lip region of a face. In one form ofpatient interface, a seal-forming structure may comprise a singleelement that surrounds both nares and a mouth region in use. Thesedifferent types of patient interfaces may be known by a variety of namesby their manufacturer including nasal masks, full-face masks, nasalpillows, nasal puffs and oro-nasal masks.

A seal-forming structure that may be effective in one region of apatient's face may be inappropriate in another region, e.g. because ofthe different shape, structure, variability and sensitivity regions ofthe patient's face. For example, a seal on swimming goggles thatoverlays a patient's forehead may not be appropriate to use on apatient's nose.

Certain seal-forming structures may be designed for mass manufacturesuch that one design fits and is comfortable and effective for a widerange of different face shapes and sizes. To the extent to which thereis a mismatch between the shape of the patient's face, and theseal-forming structure of the mass-manufactured patient interface, oneor both must adapt in order for a seal to form.

One type of seal-forming structure extends around the periphery of thepatient interface, and is intended to seal against the patient's facewhen force is applied to the patient interface with the seal-formingstructure in confronting engagement with the patient's face. Theseal-forming structure may include an air or fluid filled cushion, or amoulded or formed surface of a resilient seal element made of anelastomer such as a rubber. With this type of seal-forming structure, ifthe fit is not adequate, there will be gaps between the seal-formingstructure and the face, and additional force will be required to forcethe patient interface against the face in order to achieve a seal.

Another type of seal-forming structure incorporates a flap seal of thinmaterial positioned about the periphery of the mask so as to provide aself-sealing action against the face of the patient when positivepressure is applied within the mask. Like the previous style of sealforming portion, if the match between the face and the mask is not good,additional force may be required to achieve a seal, or the mask mayleak. Furthermore, if the shape of the seal-forming structure does notmatch that of the patient, it may crease or buckle in use, giving riseto leaks.

Another type of seal-forming structure may comprise a friction-fitelement, e.g. for insertion into a naris, however some patients findthese uncomfortable.

Another form of seal-forming structure may use adhesive to achieve aseal. Some patients may find it inconvenient to constantly apply andremove an adhesive to their face.

A range of patient interface seal-forming structure technologies aredisclosed in the following patent applications, assigned to ResMedLimited: WO 1998/004310; WO 2006/074513; WO 2010/135785.

One form of nasal pillow is found in the Adam Circuit manufactured byPuritan Bennett. Another nasal pillow, or nasal puff is the subject ofU.S. Pat. No. 4,782,832 (Trimble et al.), assigned to Puritan-BennettCorporation.

ResMed Limited has manufactured the following products that incorporatenasal pillows: SWIFT™ nasal pillows mask, SWIFT™ II nasal pillows mask,SWIFT™ LT nasal pillows mask, SWIFT™ FX nasal pillows mask and MIRAGELIBERTY™ full-face mask. The following patent applications, assigned toResMed Limited, describe examples of nasal pillows masks: InternationalPatent Application WO2004/073778 (describing amongst other thingsaspects of the ResMed Limited SWIFT™ nasal pillows), US PatentApplication 2009/0044808 (describing amongst other things aspects of theResMed Limited SWIFT™ LT nasal pillows); International PatentApplications WO 2005/063328 and WO 2006/130903 (describing amongst otherthings aspects of the ResMed Limited MIRAGE LIBERTY™ full-face mask);International Patent Application WO 2009/052560 (describing amongstother things aspects of the ResMed Limited SWIFT™ FX nasal pillows).

2.2.3.1.2 Positioning and Stabilising

A seal-forming structure of a patient interface used for positive airpressure therapy is subject to the corresponding force of the airpressure to disrupt a seal. Thus a variety of techniques have been usedto position the seal-forming structure, and to maintain it in sealingrelation with the appropriate portion of the face.

One technique is the use of adhesives. See for example US PatentApplication Publication No. US 2010/0000534. However, the use ofadhesives may be uncomfortable for some.

Another technique is the use of one or more straps and/or stabilisingharnesses. Many such harnesses suffer from being one or more ofill-fitting, bulky, uncomfortable and awkward to use.

2.2.3.1.3 Pressurised Air Conduit

In one type of treatment system, a flow of pressurised air is providedto a patient interface through a conduit in an air circuit that fluidlyconnects to the patient interface so that, when the patient interface ispositioned on the patient's face during use, the conduit extends out ofthe patient interface forwards away from the patient's face. This maysometimes be referred to as an “elephant trunk” style of interface.

Some patients find such interfaces to be unsightly and are consequentlydeterred from wearing them, reducing patient compliance. Additionally,conduits connecting to an interface at the front of a patient's face maysometimes be vulnerable to becoming tangled up in bed clothes.

2.2.3.1.4 Pressurised Air Conduit Used for Positioning/Stabilising theSeal-Forming Structure

An alternative type of treatment system which seeks to address theseproblems comprises a patient interface in which a tube that deliverspressurised air to the patient's airways also functions as part of theheadgear to position and stabilise the seal-forming portion of thepatient interface to the appropriate part of the patient's face. Thistype of patient interface may be referred to as incorporating ‘headgeartubing’ or ‘conduit headgear’. Such patient interfaces allow the conduitin the air circuit providing the flow of pressurised air from arespiratory pressure therapy device to connect to the patient interfacein a position other than in front of the patient's face. One example ofsuch a treatment system is disclosed in US Patent Publication No.2007/0246043, the contents of which are incorporated herein byreference, in which the conduit connects to a tube in the patientinterface through a port positioned in use on top of the patient's head.

The Philips DreamWear™ mask includes such headgear tubing. The length ofthe DreamWear™ headgear tubes cannot be adjusted. Consequently, theDreamWear™ headgear is supplied in three different sizes to cater fordifferent sized patient faces. Providing a greater number of differentsizes may increase the complexity and cost to manufacture the headgearand may result in larger packaging. Additionally, a supply of discretelysized masks may limit the extent to which differently sized patientheads can be accommodated. There may be a greater chance of somepatients being unable to achieve what they consider a “perfect” fit ifforced to choose between discrete sizes that are not adjustable inlength.

Patient interfaces incorporating headgear tubing may provide someadvantages, for example avoiding a conduit connecting to the patientinterface at the front of a patient's face, which may be unsightly andobtrusive. However, it is desirable for patient interfaces incorporatingheadgear tubing to be comfortable for a patient to wear over a prolongedduration when the patient is asleep while forming an effective seal withthe patient's face.

2.2.3.2 Respiratory Pressure Therapy (RPT) Device

A respiratory pressure therapy (RPT) device may be used individually oras part of a system to deliver one or more of a number of therapiesdescribed above, such as by operating the device to generate a flow ofair for delivery to an interface to the airways. The flow of air may bepressurised. Examples of RPT devices include a CPAP device and aventilator.

Air pressure generators are known in a range of applications, e.g.industrial-scale ventilation systems. However, air pressure generatorsfor medical applications have particular requirements not fulfilled bymore generalised air pressure generators, such as the reliability, sizeand weight requirements of medical devices. In addition, even devicesdesigned for medical treatment may suffer from shortcomings, pertainingto one or more of: comfort, noise, ease of use, efficacy, size, weight,manufacturability, cost, and reliability.

An example of the special requirements of certain RPT devices isacoustic noise.

The designer of a device may be presented with an infinite number ofchoices to make. Design criteria often conflict, meaning that certaindesign choices are far from routine or inevitable. Furthermore, thecomfort and efficacy of certain aspects may be highly sensitive tosmall, subtle changes in one or more parameters.

2.2.3.3 Humidifier

Delivery of a flow of air without humidification may cause drying ofairways. The use of a humidifier with an RPT device and the patientinterface produces humidified gas that minimizes drying of the nasalmucosa and increases patient airway comfort. In addition, in coolerclimates, warm air applied generally to the face area in and about thepatient interface is more comfortable than cold air.

A range of artificial humidification devices and systems are known,however they may not fulfil the specialised requirements of a medicalhumidifier.

Medical humidifiers are used to increase humidity and/or temperature ofthe flow of air in relation to ambient air when required, typicallywhere the patient may be asleep or resting (e.g. at a hospital). Amedical humidifier for bedside placement may be small. A medicalhumidifier may be configured to only humidify and/or heat the flow ofair delivered to the patient without humidifying and/or heating thepatient's surroundings. Room-based systems (e.g. a sauna, an airconditioner, or an evaporative cooler), for example, may also humidifyair that is breathed in by the patient, however those systems would alsohumidify and/or heat the entire room, which may cause discomfort to theoccupants. Furthermore medical humidifiers may have more stringentsafety constraints than industrial humidifiers

While a number of medical humidifiers are known, they can suffer fromone or more shortcomings. Some medical humidifiers may provideinadequate humidification, some are difficult or inconvenient to use bypatients.

2.2.3.4 Data Management

There may be clinical reasons to obtain data to determine whether thepatient prescribed with respiratory therapy has been “compliant”, e.g.that the patient has used their RPT device according to one or more“compliance rules”. One example of a compliance rule for CPAP therapy isthat a patient, in order to be deemed compliant, is required to use theRPT device for at least four hours a night for at least 21 of 30consecutive days. In order to determine a patient's compliance, aprovider of the RPT device, such as a health care provider, may manuallyobtain data describing the patient's therapy using the RPT device,calculate the usage over a predetermined time period, and compare withthe compliance rule. Once the health care provider has determined thatthe patient has used their RPT device according to the compliance rule,the health care provider may notify a third party that the patient iscompliant.

There may be other aspects of a patient's therapy that would benefitfrom communication of therapy data to a third party or external system.

Existing processes to communicate and manage such data can be one ormore of costly, time-consuming, and error-prone.

2.2.3.5 Mandibular Repositioning

A mandibular repositioning device (MRD) or mandibular advancement device(MAD) is one of the treatment options for sleep apnea and snoring. It isan adjustable oral appliance available from a dentist or other supplierthat holds the lower jaw (mandible) in a forward position during sleep.The MRD is a removable device that a patient inserts into their mouthprior to going to sleep and removes following sleep. Thus, the MRD isnot designed to be worn all of the time. The MRD may be custom made orproduced in a standard form and includes a bite impression portiondesigned to allow fitting to a patient's teeth. This mechanicalprotrusion of the lower jaw expands the space behind the tongue, putstension on the pharyngeal walls to reduce collapse of the airway anddiminishes palate vibration.

In certain examples a mandibular advancement device may comprise anupper splint that is intended to engage with or fit over teeth on theupper jaw or maxilla and a lower splint that is intended to engage withor fit over teeth on the upper jaw or mandible. The upper and lowersplints are connected together laterally via a pair of connecting rods.The pair of connecting rods are fixed symmetrically on the upper splintand on the lower splint.

In such a design the length of the connecting rods is selected such thatwhen the MRD is placed in a patient's mouth the mandible is held in anadvanced position. The length of the connecting rods may be adjusted tochange the level of protrusion of the mandible. A dentist may determinea level of protrusion for the mandible that will determine the length ofthe connecting rods.

Some MRDs are structured to push the mandible forward relative to themaxilla while other MRDs, such as the ResMed Narval CC™ MRD are designedto retain the mandible in a forward position. This device also reducesor minimises dental and temporo-mandibular joint (TMJ) side effects.Thus, it is configured to minimises or prevent any movement of one ormore of the teeth.

2.2.3.6 Vent Technologies

Some forms of treatment systems may include a vent to allow the washoutof exhaled carbon dioxide. The vent may allow a flow of gas from aninterior space of a patient interface, e.g., the plenum chamber, to anexterior of the patient interface, e.g., to ambient.

The vent may comprise an orifice and gas may flow through the orifice inuse of the mask. Many such vents are noisy. Others may become blocked inuse and thus provide insufficient washout. Some vents may be disruptiveof the sleep of a bed partner 1100 of the patient 1000, e.g. throughnoise or focussed airflow.

ResMed Limited has developed a number of improved mask venttechnologies. See International Patent Application Publication No. WO1998/034,665; International Patent Application Publication No. WO2000/078,381; U.S. Pat. No. 6,581,594; US Patent Application PublicationNo. US 2009/0050156; US Patent Application Publication No. 2009/0044808.

Table of noise of prior masks (ISO 17510- 2:2007, 10 cmH₂O pressure at 1m) A-weighted A-weighted sound power sound pressure level dB(A) dB(A)Year Mask name Mask type (uncertainty) (uncertainty) (approx.) Glue-on(*) nasal 50.9 42.9 1981 ResCare nasal 31.5 23.5 1993 standard (*)ResMed nasal 29.5 21.5 1998 Mirage ™ (*) ResMed nasal 36 (3) 28 (3) 2000UltraMirage ™ ResMed nasal 32 (3) 24 (3) 2002 Mirage Activa ™ ResMednasal 30 (3) 22 (3) 2008 Mirage Micro ™ ResMed nasal 29 (3) 22 (3) 2008Mirage ™ SoftGel ResMed nasal 26 (3) 18 (3) 2010 Mirage ™ FX ResMednasal 37 29 2004 Mirage pillows Swift ™ (*) ResMed nasal 28 (3) 20 (3)2005 Mirage pillows Swift ™ II ResMed nasal 25 (3) 17 (3) 2008 Miragepillows Swift ™ LT ResMed nasal 21 (3) 13 (3) 2014 AirFit P10 pillows (*one specimen only, measured using test method specified in ISO 3744 inCPAP mode at 10 cmH₂O)

Sound pressure values of a variety of objects are listed below

A-weighted sound Object pressure dB(A) Notes Vacuum cleaner: Nilfisk 68ISO 3744 at Walter Broadly Litter Hog: 1 m distance B+ GradeConversational speech 60 1 m distance Average home 50 Quiet library 40Quiet bedroom at night 30 Background in TV studio 20

2.2.4 Screening, Diagnosis, and Monitoring Systems

Polysomnography (PSG) is a conventional system for diagnosis andmonitoring of cardio-pulmonary disorders, and typically involves expertclinical staff to apply the system. PSG typically involves the placementof 15 to 20 contact sensors on a patient in order to record variousbodily signals such as electroencephalography (EEG), electrocardiography(ECG), electrooculograpy (EOG), electromyography (EMG), etc. PSG forsleep disordered breathing has involved two nights of observation of apatient in a clinic, one night of pure diagnosis and a second night oftitration of treatment parameters by a clinician. PSG is thereforeexpensive and inconvenient. In particular it is unsuitable for homescreening/diagnosis/monitoring of sleep disordered breathing.

Screening and diagnosis generally describe the identification of acondition from its signs and symptoms. Screening typically gives atrue/false result indicating whether or not a patient's SDB is severeenough to warrant further investigation, while diagnosis may result inclinically actionable information. Screening and diagnosis tend to beone-off processes, whereas monitoring the progress of a condition cancontinue indefinitely. Some screening/diagnosis systems are suitableonly for screening/diagnosis, whereas some may also be used formonitoring.

Clinical experts may be able to screen, diagnose, or monitor patientsadequately based on visual observation of PSG signals. However, thereare circumstances where a clinical expert may not be available, or aclinical expert may not be affordable. Different clinical experts maydisagree on a patient's condition. In addition, a given clinical expertmay apply a different standard at different times.

3 BRIEF SUMMARY OF THE TECHNOLOGY

The present technology is directed towards providing medical devicesused in the screening, diagnosis, monitoring, amelioration, treatment,or prevention of respiratory disorders having one or more of improvedcomfort, cost, efficacy, ease of use and manufacturability.

A first aspect of the present technology relates to apparatus used inthe screening, diagnosis, monitoring, amelioration, treatment orprevention of a respiratory disorder.

Another aspect of the present technology relates to methods used in thescreening, diagnosis, monitoring, amelioration, treatment or preventionof a respiratory disorder.

An aspect of certain forms of the present technology is to providemethods and/or apparatus that improve the compliance of patients withrespiratory therapy.

One aspect of the present technology comprises a patient interface fordelivery of a supply of pressurised breathable gas to an entrance of apatient's airways.

Another aspect of the present technology is directed to a patientinterface that may comprise: a plenum chamber; a seal-forming structure;and a positioning and stabilising structure. The patient interface mayfurther comprise a vent structure. The patient may further be configuredto leave the patient's mouth uncovered, or if the seal-forming structureis configured to seal around the patient's nose and mouth, the patientinterface may be further configured to allow the patient to breath fromambient in the absence of a flow of pressurised air through the plenumchamber inlet port.

Another aspect of the present technology is directed to a patientinterface that includes: a plenum chamber; a seal-forming structure; avent structure; and a positioning and stabilising structure to provide aforce to hold a seal-forming structure in a therapeutically effectiveposition on a patient's head. The positioning and stabilising structureincluding at least one gas delivery tube to receive the flow of air froma connection port and to deliver the flow of air to the entrance of thepatient's airways via the seal-forming structure, the gas delivery tubebeing constructed and arranged to contact, in use, at least a region ofthe patient's head superior to an otobasion superior of the patient'shead.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

at least one gas delivery tube to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, the gas delivery tube being constructed and arranged tocontact, in use, at least a region of the patient's head superior to anotobasion superior of the patient's head, the gas delivery tubecomprising:

-   -   a tube wall defining a hollow interior through which air is able        to flow to the seal-forming structure, the tube wall having an        extendable portion configured to be extended to vary a length of        the gas delivery tube;    -   wherein the extendable portion comprises an extension stiffness        within the range of 0.2 to 0.35 N/mm.

In examples of any of the aspects of any of the preceding paragraphs:(a) the extension stiffness of the extendable portion is within therange of 0.25 to 0.3 N/mm; (b) the pair of gas delivery tubes comprise acombined unextended length, measured along a centreline of a side of thepair of tubes configured to be patient-facing in use, within the rangeof 500 to 535 mm; (c) the combined unextended length is within the rangeof 510 to 525 mm; (d) the combined unextended length is within the rangeof 512 to 522 mm; (e) the pair of gas delivery tubes comprise a combinedunextended length, measured along a centreline of a side of the pair oftubes configured to be patient-facing in use, within the range of 460 to500 mm; (f) the combined unextended length is within the range of 470 to490 mm; (g) the combined unextended length is within the range of 475 to485 mm; (h) the gas delivery tubes form a loop around the patient's headtogether with a cushion module, the loop having an unextended length,measured along a centreline of a side of the gas delivery tubes andcushion module configured to be patient-facing in use, within the rangeof 510 to 610 mm; (i) the unextended length of the loop is within therange of 528 to 548 mm; (j), the unextended length of the loop is withinthe range of 535 to 541 mm; (k) the unextended length of the loop iswithin the range of 534 to 554 mm (l) the unextended length of the loopis within the range of 539 to 549 mm; (m) the unextended length of theloop is within the range of 541 to 561 mm; (n) the unextended length ofthe loop is within the range of 546 to 556 mm; (o) the unextended lengthof the loop is within the range of 564 to 584 mm; (p) the unextendedlength of the loop is within the range of 571 to 581 mm; (q) theunextended length of the loop is within the range of 577 to 597 mm;and/or (r) the unextended length of the loop is within the range of 582to 592 mm.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

at least one gas delivery tube to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, the at least one gas delivery tube being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, the at leastone gas delivery tube comprising:

-   -   a superior tube portion configured, in use, to overlie a        superior region of the patient's head, the superior tube portion        comprising:        -   a first end configured, in use, to overlie a superior            portion of the patient's head at or proximate the sagittal            plane of the patient's head;        -   a second end configured, in use, to overlie a side portion            of the patient's head;        -   a stiffened portion between the first end and the second end            configured to provide a higher resistance to relative            movement between the first end and the second end in an            anterior and/or posterior direction than in a superior            and/or inferior direction in use;    -   an inferior tube portion connected between the second end of the        superior tube portion and the seal-forming structure.

In examples of any of the aspects of any of the preceding paragraphs:(a) each superior tube portion comprises two stiffened portions; (b) thestiffened portions are provided to one or both of a side of the superiortube portion configured to be anterior in use and a side of the superiortube portion configured to be posterior in use; (c) the superior tubeportion comprises an extendable portion; (d) the extendable portioncomprises an extendable concertina structure formed in a tube wall ofthe gas delivery tube; (e) the extendable concertina structure comprisesplurality of folds in the tube wall alternatingly forming a plurality ofridges and a plurality of grooves; (f) the stiffened portion comprises aplurality of connecting portions formed in the tube wall, each of theplurality of connecting portions connecting a pair of adjacent ridges;and/or (g) the stiffened portions are integrally formed with thesuperior tube portion.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

at least one gas delivery tube to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, the at least one gas delivery tube being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, the at leastone gas delivery tube comprising a tube wall having an extendableconcertina structure comprising:

-   -   a plurality of folds in the tube wall alternatingly forming a        plurality of ridges and a plurality of grooves, the folds able        to be at least partially unfolded to increase a separation of        the ridges to elongate the extendable concertina structure; and    -   one or more ridge connecting portions provided to the tube wall,        each of the one or more ridge connecting portions connecting two        or more adjacent ridges of the plurality of ridges and being        configured to resist the separation of the ridges.

In examples of any of the aspects of any of the preceding paragraphs:(a) each pair of adjacent ridges is connected by at least one ridgeconnecting portion of the one or more ridge connecting portions; (b) oneor more pairs of adjacent ridges are connected by two ridge connectingportions; (c) each pair of adjacent ridges is connected by two ridgeconnecting portions; (d) one or more of the ridge connecting portions islocated on a side of the gas delivery tube configured to beanterior-facing in use; (e) one or more of the ridge connecting portionsis located on a side of the gas delivery tube configured to beposterior-facing in use; (f) each of the ridge connecting portions isspaced centrally between a side of the gas delivery tube configured tobe inferior-facing in use and a side of the gas delivery tube configuredto be superior-facing in use; (g) each pair of adjacent ridges isconnected by one of the ridge connecting portion located on the side ofthe gas delivery tube configured to be anterior-facing in use; (h) eachpair of adjacent ridges is connected by one of the ridge connectingportion located on the side of the gas delivery tube configured to beposterior-facing; (i) the gas delivery tube comprises a non-extendableportion having an outer surface and each of the plurality of grooves isformed as a depression with respect to the outer surface of thenon-extendable portion; (j) the gas delivery tube comprises anon-extendable portion having an outer surface and each of the pluralityof ridges is raised with respect to the outer surface of thenon-extendable portion; (k) each of the plurality of grooves is locatedbetween a respective pair of ridge connecting portions, each ridgeconnecting portion of the pair of ridge connecting portions beinglocated at a respective end of the respective groove; (l) each of theplurality of grooves comprises a groove depth and each of the pluralityof ridge connecting portions comprises a ridge connecting portionheight, the groove depth of each respective groove being equal to theridge connecting portion height of each of the respective pair of ridgeconnecting portions located at the ends of the respective groove; (m)each ridge connection portion is an integrally formed portion of thetube wall; (n) the plurality of ridges, the plurality of grooves and theplurality of ridge connecting portions are integrally formed; (o) eachof the plurality of ridges comprises a curved ridge portion central tothe respective ridge; (p) each of the plurality of grooves comprises acurved groove portion central to the respective groove; (q) each of theplurality of ridges comprises a pair of straight ridge portions providedat opposite ends of the respective ridge; (r) each of the plurality ofridge connecting portions connects the respective adjacent pair ofridges at the straight ridge portions of the ridge; (s) the gas deliverytube at the extendable concertina structure comprises a cross-sectionhaving a width and a height, the width being aligned in usesubstantially with the anterior-posterior directions, the width beinglarger than the height; (t) the width is at least twice as large as theheight; and/or (u) the positioning and stabilising structure comprisestwo gas delivery tubes fluidly connected between the connection port andthe seal-forming structure, each gas delivery tube extending, in use,across one of the patient's cheek regions, the two gas delivery tubesbeing on different sides of the patient's head.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

at least one gas delivery tube to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, the at least one gas delivery tube being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, the at leastone gas delivery tube comprising a tube wall having a hollow interiorand having an extendable concertina structure provided along a length ofthe gas delivery tube, the extendable concertina structure comprising:

-   -   a plurality of folds in the tube wall forming a first        alternating series of ridges and grooves along a        non-patient-contacting side of the gas delivery tube and a        second alternating series of ridges and grooves along a        patient-contacting side of the gas delivery tube;    -   wherein the first alternating series of ridges and grooves has a        lesser extension stiffness than the second alternating series of        ridges and grooves.

In examples: (a) the plurality of folds form, interior to the gasdelivery tube, interior ridges and interior grooves forming the firstalternating series of ridges and grooves and the second alternatingseries of ridges and grooves; (b) each one of the interior grooves ofthe first alternating series is provided opposite a respective one ofthe interior grooves of the second alternating series across theinterior of the gas delivery tube to form a plurality of opposing groovepairs, each opposing groove pair comprising: a first interior groove,being one interior groove of the first alternating series; and a secondinterior groove, being one interior groove of the second alternatingseries; wherein the first interior groove comprises a greater groovedepth than the second interior groove; (c) the tube wall comprises agreater material thickness at a base of the second interior groove ofeach opposing groove pair than at a base of the first interior groove ofthe respective opposing groove pair; (d) the material thickness of thetube wall at the base of each interior groove of the second alternatingseries reduces along the length of the gas delivery tube from a firstend proximate the connection port to a second end; (e) the materialthickness of the tube wall at the base of each interior groove of thefirst alternating series is substantially constant along the length ofthe gas delivery tube; (f) the groove depths of the interior grooves ofthe first and second alternating series of interior ridges and interiorgrooves reduce along the length of the gas delivery tube from a firstend adjacent the connection port to a second end; and/or (g) the firstinterior groove of each opposed groove pair is joined to the secondinterior groove of the respective opposed groove pair at sides of thegas delivery tube between the non-patient-contacting side and thepatient-contacting side.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

a pair of gas delivery tubes to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, each of the pair of gas delivery tubes being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, and each gasdelivery tube comprising:

-   -   a tube wall defining a hollow interior along the length of the        gas delivery tube;    -   a tab connected to the tube wall and configured, in use, to be        located superior to the otobasion superior of the patient's        head; and    -   a slit formed in the tab, the slit spaced posteriorly in use        from the tube wall, the slit comprising a superior end and an        inferior end,    -   wherein the superior end of the slit is spaced further from the        tube wall than the inferior end of the slit; and

a strap constructed and arranged to contact, in use, a region of thepatient's head inferior to or overlaying an occipital bone of thepatient's head, the strap being configured to connect to and between theslits.

In examples of any of the aspects of any of the preceding paragraphs:(a) each tab is integrally formed with a respective tube wall; (b) eachtab has a superior edge and an inferior edge, the superior edge beinglonger than the inferior edge; (c) the inferior end of the slit isspaced from the tube wall by at least 5 mm; (d) the inferior end of theslit is spaced from the tube wall at least 7 mm; (e) the inferior end ofthe slit is spaced from the tube wall by 8 mm or more; (f) the superiorend of the slit is spaced from the tube wall by at least 8 mm; (g) thesuperior end of the slit is spaced from the tube wall by at least 10 mm;(h) the superior end of the slit is spaced from the tube wall by 12 mmor more; (i) a midpoint along the slit is spaced from the tube wall by aspacing within the range of 5 mm to 30 mm; (j) the spacing is within therange of 7 mm to 20 mm; (k) the spacing is within the range of 8 mm to15 mm; (l) the spacing is within the range of 9 to 11 mm; (m) each gasdelivery tube comprises an extendable tube section located superior inuse to the tab of the respective gas delivery tube and a non-extendabletube section located inferior in use to the tab of the respective gasdelivery tube; (n) each tab is joined to the tube wall of the respectivegas delivery tube at the non-extendable tube section; (o) each slit isarcuate between the superior end and the inferior end; (p) each slit isstraight between the superior end and the inferior end; and/or (q) eachslit is oriented perpendicular to the direction from the slit of a strapanchor region against which the strap is anchored around the patient'shead.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

a pair of gas delivery tubes to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, each of the pair of gas delivery tubes being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, and each gasdelivery tube comprising:

-   -   a tube wall configured, in use, to overlie the patient's head        along a path from a superior portion of the patient's head to        the seal forming structure passing between an eye and an ear of        the patient;    -   a tab connected to the tube wall and configured, in use, to be        located superior to the otobasion superior of the patient's        head; and    -   a slit formed in the tab and spaced posteriorly in use from a        slit-adjacent portion of the path of the tube wall;    -   wherein the slit has a posterosuperior-anteroinferior        orientation in use and forms an oblique angle with a tangent of        the path of the tube wall at the slit-adjacent portion; and

a strap constructed and arranged to contact, in use, a region of thepatient's head inferior to or overlaying an occipital bone of thepatient's head, the strap being configured to connect to and between theslits.

In examples of any of the aspects of any of the preceding paragraphs:(a) each tab is integrally formed with a respective one of the tubewalls; (b) each tab has a superior edge and an inferior edge in use, thesuperior edge being longer than the inferior edge; (c) each gas deliverytube comprises an extendable tube section superior to the tab of therespective gas delivery tube in use and a non-extendable tube sectioninferior to the tab of the respective gas delivery tube in use; (d) eachtab is connected to the tube wall of the respective gas delivery tube atthe non-extendable tube section; (e) each slit is arcuate between asuperior end and an inferior end of the slit; (f) each slit is straightbetween a superior end and an inferior end of the slit; (g) an inferiorend of the slit is spaced from the tube wall by at least 5 mm; (h) theinferior end of the slit is spaced from the tube wall at least 7 mm (i)the inferior end of the slit is spaced from the tube wall by 8 mm ormore; (j) a superior end of the slit is spaced from the tube wall by atleast 8 mm; (k) the superior end of the slit is spaced from the tubewall by at least 10 mm; (l) the superior end of the slit is spaced fromthe tube wall by 12 mm or more; (m) the oblique angle is in the range of10 to 20 degrees; (n) the oblique angle is in the range of 12 to 18degrees; and/or (o) each slit is oriented perpendicular to the directionfrom the slit of a strap anchor region against which the strap isanchored around the patient's head.

According to one aspect of the present technology there is provided apositioning and stabilising structure to provide a force to hold aseal-forming structure in a therapeutically effective position on apatient's head, the seal-forming structure constructed and arranged toform a seal with a region of the patient's face surrounding an entranceto the patient's airways for sealed delivery of a flow of air at atherapeutic pressure of at least 6 cmH₂O above ambient air pressurethroughout the patient's respiratory cycle in use, the positioning andstabilising structure comprising:

a pair of gas delivery tubes to receive the flow of air from aconnection port on top of the patient's head and to deliver the flow ofair to the entrance of the patient's airways via the seal-formingstructure, each of the pair of gas delivery tubes being constructed andarranged to contact, in use, at least a region of the patient's headsuperior to an otobasion superior of the patient's head, and each gasdelivery tube comprising:

-   -   a tube wall configured to overlie the patient's head from a        superior portion of the patient's head to the seal forming        structure passing between an eye and an ear of the patient; and    -   a tab connected to the tube wall and located superior to the        otobasion superior of the patient's head in use;    -   an eyelet formed in the tab and located posteriorly to the tube        wall in use;    -   a trough formed in the tab and located posteriorly to the        eyelet; and

a strap constructed and arranged to contact, in use, a region of thepatient's head inferior to or overlaying an occipital bone of thepatient's head, the strap being configured to connect to and between theeyelets of the pair of gas delivery tubes and to lie within the troughsformed in the tabs in use.

In examples of any of the aspects of any of the preceding paragraphs:(a) the trough is formed in the tab between the eyelet and a posteriorside of the tab; (b) the tab comprises an outwardly facing surface andthe trough comprises a substantially planar surface formed as adepression with respect to the outwardly facing surface; (c) the troughis formed by a portion of the tab having a reduced material thickness incomparison to other portions of the tab; (d) the trough comprises alength approximately equal to the width of the strap; and/or (e) theeyelet is in the form of a slit.

According to one aspect of the present technology, there is provided apatient interface comprising:

a plenum chamber pressurisable to a therapeutic pressure of at least 6cmH₂O above ambient air pressure, said plenum chamber including a plenumchamber inlet port sized and structured to receive a flow of air at thetherapeutic pressure for breathing by a patient,

a seal-forming structure constructed and arranged to form a seal with aregion of the patient's face surrounding an entrance to the patient'sairways, said seal-forming structure having a hole therein such that theflow of air at said therapeutic pressure is delivered to at least anentrance to the patient's nares, the seal-forming structure constructedand arranged to maintain said therapeutic pressure in the plenum chamberthroughout the patient's respiratory cycle in use;

the positioning and stabilising structure according to any one of theabove aspects; and

a vent structure to allow a continuous flow of gases exhaled by thepatient from an interior of the plenum chamber to ambient, said ventstructure being sized and shaped to maintain the therapeutic pressure inthe plenum chamber in use;

wherein the patient interface is configured to allow the patient tobreath from ambient through their mouth in the absence of a flow ofpressurised air through the plenum chamber inlet port, or the patientinterface is configured to leave the patient's mouth uncovered.

Another aspect of certain forms of the present technology is a systemfor treating a respiratory disorder comprising a patient interfaceaccording to any one or more of the other aspects of the presenttechnology, an air circuit and a source of air at positive pressure.

Another aspect of one form of the present technology is a patientinterface that is moulded or otherwise constructed with a perimetershape which is complementary to that of an intended wearer.

Another aspect of certain forms of the present technology is a patientinterface comprising a seal-forming structure configured to leave thepatient's mouth uncovered in use.

Another aspect of certain forms of the present technology is a patientinterface comprising a seal-forming structure configured so that no partof the seal-forming structure enters the mouth in use.

Another aspect of certain forms of the present technology is a patientinterface comprising a seal-forming structure configured so that theseal-forming structure does not extend internally of the patient'sairways.

Another aspect of certain forms of the present technology is a patientinterface comprising a seal-forming structure configured so that theseal-forming structure does not extend below a mental protuberanceregion in use.

Another aspect of certain forms of the present technology is a patientinterface constructed and arranged to leave a patient's eyes uncoveredin use.

Another aspect of certain forms of the present technology is a patientinterface constructed and arranged to allow a patient to breathe ambientair in the event of a power failure.

Another aspect of certain forms of the present technology is a patientinterface comprising a seal forming structure configured to form a sealon an underside of a patient's nose without contacting a nasal bridgeregion of the patient's nose.

Another aspect of certain forms of the present technology is a patientinterface comprising a vent and a plenum chamber, wherein the patientinterface is constructed and arranged so that gases from an interior ofthe plenum chamber may pass to ambient via the vent.

Another aspect of certain forms of the present technology is a patientinterface constructed and arranged so that a patient may lie comfortablyin a side or lateral sleeping position, in use of the patient interface.

Another aspect of certain forms of the present technology is a patientinterface constructed and arranged so that a patient may lie comfortablyin a supine sleeping position, in use of the patient interface.

Another aspect of certain forms of the present technology is a patientinterface constructed and arranged so that a patient may lie comfortablyin a prone sleeping position, in use of the patient interface.

An aspect of certain forms of the present technology is a medical devicethat is easy to use, e.g. by a person who does not have medicaltraining, by a person who has limited dexterity, vision or by a personwith limited experience in using this type of medical device.

An aspect of one form of the present technology is a patient interfacethat may be washed in a home of a patient, e.g., in soapy water, withoutrequiring specialised cleaning equipment.

Of course, portions of the aspects may form sub-aspects of the presenttechnology. Also, various ones of the sub-aspects and/or aspects may becombined in various manners and also constitute additional aspects orsub-aspects of the present technology.

Other features of the technology will be apparent from consideration ofthe information contained in the following detailed description,abstract, drawings and claims.

4 BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

4.1 Treatment Systems

FIG. 1A shows a system including a patient 1000 wearing a patientinterface 3000, in the form of nasal pillows, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device4000 is humidified in a humidifier 5000, and passes along an air circuit4170 to the patient 1000. A bed partner 1100 is also shown. The patientis sleeping in a supine sleeping position.

FIG. 1B shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal mask, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device ishumidified in a humidifier 5000, and passes along an air circuit 4170 tothe patient 1000.

FIG. 1C shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a full-face mask, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000. The patient is sleeping in a sidesleeping position.

4.2 Respiratory System and Facial Anatomy

FIG. 2A shows an overview of a human respiratory system including thenasal and oral cavities, the larynx, vocal folds, oesophagus, trachea,bronchus, lung, alveolar sacs, heart and diaphragm.

FIG. 2B shows a view of a human upper airway including the nasal cavity,nasal bone, lateral nasal cartilage, greater alar cartilage, nostril,lip superior, lip inferior, larynx, hard palate, soft palate,oropharynx, tongue, epiglottis, vocal folds, oesophagus and trachea.

FIG. 2C is a front view of a face with several features of surfaceanatomy identified including the lip superior, upper vermilion, lowervermilion, lip inferior, mouth width, endocanthion, a nasal ala,nasolabial sulcus and cheilion. Also indicated are the directionssuperior, inferior, radially inward and radially outward.

FIG. 2D is a side view of a head with several features of surfaceanatomy identified including glabella, sellion, pronasale, subnasale,lip superior, lip inferior, supramenton, nasal ridge, alar crest point,otobasion superior and otobasion inferior. Also indicated are thedirections superior & inferior, and anterior & posterior.

FIG. 2E is a further side view of a head. The approximate locations ofthe Frankfort horizontal and nasolabial angle are indicated. The coronalplane is also indicated.

FIG. 2F shows a base view of a nose with several features identifiedincluding naso-labial sulcus, lip inferior, upper Vermilion, naris,subnasale, columella, pronasale, the major axis of a naris and themidsagittal plane.

FIG. 2G shows a side view of the superficial features of a nose.

FIG. 2H shows subcutaneal structures of the nose, including lateralcartilage, septum cartilage, greater alar cartilage, lesser alarcartilage, sesamoid cartilage, nasal bone, epidermis, adipose tissue,frontal process of the maxilla and fibrofatty tissue.

FIG. 2I shows a medial dissection of a nose, approximately severalmillimeters from the midsagittal plane, amongst other things showing theseptum cartilage and medial crus of greater alar cartilage.

FIG. 2J shows a front view of the bones of a skull including thefrontal, nasal and zygomatic bones. Nasal concha are indicated, as arethe maxilla, and mandible.

FIG. 2K shows a lateral view of a skull with the outline of the surfaceof a head, as well as several muscles. The following bones are shown:frontal, sphenoid, nasal, zygomatic, maxilla, mandible, parietal,temporal and occipital. The mental protuberance is indicated. Thefollowing muscles are shown: digastricus, masseter, sternocleidomastoidand trapezius.

FIG. 2L shows an anterolateral view of a nose.

4.3 Patient Interface

FIG. 3A shows a patient interface in the form of a nasal mask inaccordance with one form of the present technology.

FIG. 3B shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a positive sign, and a relatively large magnitude whencompared to the magnitude of the curvature shown in FIG. 3C.

FIG. 3C shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a positive sign, and a relatively small magnitude whencompared to the magnitude of the curvature shown in FIG. 3B.

FIG. 3D shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a value of zero.

FIG. 3E shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a negative sign, and a relatively small magnitude whencompared to the magnitude of the curvature shown in FIG. 3F.

FIG. 3F shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a negative sign, and a relatively large magnitude whencompared to the magnitude of the curvature shown in FIG. 3E.

FIG. 3G shows a cushion for a mask that includes two pillows. Anexterior surface of the cushion is indicated. An edge of the surface isindicated. Dome and saddle regions are indicated.

FIG. 3H shows a cushion for a mask. An exterior surface of the cushionis indicated. An edge of the surface is indicated. A path on the surfacebetween points A and B is indicated. A straight line distance between Aand B is indicated. Two saddle regions and a dome region are indicated.

FIG. 3I shows the surface of a structure, with a one dimensional hole inthe surface. The illustrated plane curve forms the boundary of a onedimensional hole.

FIG. 3J shows a cross-section through the structure of FIG. 3I. Theillustrated surface bounds a two dimensional hole in the structure ofFIG. 3I.

FIG. 3K shows a perspective view of the structure of FIG. 3I, includingthe two dimensional hole and the one dimensional hole. Also shown is thesurface that bounds a two dimensional hole in the structure of FIG. 3I.

FIG. 3L shows a mask having an inflatable bladder as a cushion.

FIG. 3M shows a cross-section through the mask of FIG. 3L, and shows theinterior surface of the bladder. The interior surface bounds the twodimensional hole in the mask.

FIG. 3N shows a further cross-section through the mask of FIG. 3L. Theinterior surface is also indicated.

FIG. 3O illustrates a left-hand rule.

FIG. 3P illustrates a right-hand rule.

FIG. 3Q shows a left ear, including the left ear helix.

FIG. 3R shows a right ear, including the right ear helix.

FIG. 3S shows a right-hand helix.

FIG. 3T shows a view of a mask, including the sign of the torsion of thespace curve defined by the edge of the sealing membrane in differentregions of the mask.

FIG. 3U shows a view of a plenum chamber 3200 showing a sagittal planeand a mid-contact plane.

FIG. 3V shows a view of a posterior of the plenum chamber of FIG. 3U.The direction of the view is normal to the mid-contact plane. Thesagittal plane in FIG. 3V bisects the plenum chamber into left-hand andright-hand sides.

FIG. 3W shows a cross-section through the plenum chamber of FIG. 3V, thecross-section being taken at the sagittal plane shown in FIG. 3V. A‘mid-contact’ plane is shown. The mid-contact plane is perpendicular tothe sagittal plane. The orientation of the mid-contact plane correspondsto the orientation of a chord which lies on the sagittal plane and justtouches the cushion of the plenum chamber at two points on the sagittalplane: a superior point and an inferior point. Depending on the geometryof the cushion in this region, the mid-contact plane may be a tangent atboth the superior and inferior points.

FIG. 3X shows the plenum chamber 3200 of FIG. 3U in position for use ona face. The sagittal plane of the plenum chamber 3200 generallycoincides with the midsagittal plane of the face when the plenum chamberis in position for use. The mid-contact plane corresponds generally tothe ‘plane of the face’ when the plenum chamber is in position for use.In FIG. 3X the plenum chamber 3200 is that of a nasal mask, and thesuperior point sits approximately on the sellion, while the inferiorpoint sits on the lip superior.

4.4 RPT Device

FIG. 4A shows an RPT device in accordance with one form of the presenttechnology.

FIG. 4B is a schematic diagram of the pneumatic path of an RPT device inaccordance with one form of the present technology. The directions ofupstream and downstream are indicated with reference to the blower andthe patient interface. The blower is defined to be upstream of thepatient interface and the patient interface is defined to be downstreamof the blower, regardless of the actual flow direction at any particularmoment. Items which are located within the pneumatic path between theblower and the patient interface are downstream of the blower andupstream of the patient interface.

4.5 Humidifier

FIG. 5A shows an isometric view of a humidifier in accordance with oneform of the present technology.

FIG. 5B shows an isometric view of a humidifier in accordance with oneform of the present technology, showing a humidifier reservoir 5110removed from the humidifier reservoir dock 5130.

4.6 Breathing Waveforms

FIG. 6A shows a model typical breath waveform of a person whilesleeping.

4.7 Screening, Diagnosis and Monitoring Systems

FIG. 7A shows a patient undergoing polysomnography (PSG). The patient issleeping in a supine sleeping position.

FIG. 7B shows a monitoring apparatus for monitoring the condition of apatient. The patient is sleeping in a supine sleeping position.

4.8 Particular Examples of the Present Technology

FIG. 8A is a perspective view illustration of a patient interface 3000according to one example of the present technology while worn by apatient 1000.

FIG. 8B is a front view illustration of the patient interface 3000 shownin FIG. 8A.

FIG. 8C is a side view illustration of the patient interface 3000 shownin FIG. 8A.

FIG. 8D is another side view illustration of the patient interface 3000shown in FIG. 8A.

FIG. 9A is a perspective view illustration of the patient interface 3000of FIG. 8A in isolation.

FIG. 9B is a rear perspective view illustration of the patient interface3000 of FIG. 8A in isolation.

FIG. 9C is a top view illustration of the patient interface 3000 of FIG.8A in isolation.

FIG. 10A shows a plan view of components of a positioning andstabilising structure 3300 according to one example of the presenttechnology.

FIG. 10B shows a cross section view B-B of a portion of the positioningand stabilising structure 3300 of FIG. 10A.

FIG. 10C shows a cross section view C-C of a non-extendable portion ofthe positioning and stabilising structure 3300 of FIG. 10A.

FIG. 10D shows a plan view of a portion of an extendable portion of thepositioning and stabilising structure 3300 of FIG. 10A.

FIG. 10E shows a cross section view E-E of an extendable portion of thepositioning and stabilising structure the 3300 of FIG. 10D.

FIG. 10F shows a front view of a portion of an extendable portion of thepositioning and stabling structure 3300 of FIG. 10A.

FIG. 10G shows a front view of an extendable portion of the positioningand stabilising structure 3300 of FIG. 10A in a straightenedconfiguration.

FIG. 10H shows a front view of the extendable portion shown in FIG. 10Gin a curved configuration.

FIG. 10I shows a perspective view of the extendable portion shown inFIG. 10G in a curved configuration.

FIG. 10J shows a top view of the extendable portion shown in FIG. 10G ina curved configuration.

FIG. 11A shows a side view of a tab of the positioning and stabilisingstructure 3300 of FIG. 10A.

FIG. 11B shows another side view of a tab of the positioning andstabilising structure 3300 of FIG. 10A

FIG. 11C is a perspective view of the tab of FIG. 11A.

FIG. 12A is perspective view of a patient interface 3000 according toanother example of the present technology while worn by a patient 1000.

FIG. 12B is a perspective view of the patient interface 3000 of FIG. 12Ain isolation.

FIG. 12C is a front view of the patient interface 3000 of FIG. 12A.

FIG. 12D is a rear view of the patient interface 3000 of FIG. 12A.

FIG. 12E is a plan view of the patient interface 3000 of FIG. 12A.

FIG. 12F is a side view of the patient interface 3000 of FIG. 12A.

FIG. 13 is a perspective view of a portion of a positioning andstabilising structure 3300 of a patient interface according to anotherexample of the present technology.

5 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

Before the present technology is described in further detail, it is tobe understood that the technology is not limited to the particularexamples described herein, which may vary. It is also to be understoodthat the terminology used in this disclosure is for the purpose ofdescribing only the particular examples discussed herein, and is notintended to be limiting.

The following description is provided in relation to various exampleswhich may share one or more common characteristics and/or features. Itis to be understood that one or more features of any one example may becombinable with one or more features of another example or otherexamples. In addition, any single feature or combination of features inany of the examples may constitute a further example.

5.1 Therapy

In one form as shown in FIG. 1A, the present technology comprises amethod for treating a respiratory disorder comprising the step ofapplying positive pressure to the entrance of the airways of a patient1000.

In certain examples of the present technology, a supply of air atpositive pressure is provided to the nasal passages of the patient viaone or both nares.

In certain examples of the present technology, mouth breathing islimited, restricted or prevented.

5.2 Treatment Systems

In one form, the present technology comprises an apparatus or device fortreating a respiratory disorder. The apparatus or device may comprise anRPT device 4000 for supplying pressurised air to the patient 1000 via anair circuit 4170 to a patient interface 3000. FIGS. 1A, 1B and 1Cillustrate treatment systems that utilise patent interfaces 3000 withRPT devices 4000 and humidifiers 5000.

5.3 Patient Interface

With reference to FIG. 3A, a patient interface 3000 in accordance withone aspect of the present technology comprises the following functionalaspects: a seal-forming structure 3100, a plenum chamber 3200, apositioning and stabilising structure 3300, a vent 3400, one form ofconnection port 3600 for connection to air circuit 4170, and a foreheadsupport 3700. In some forms a functional aspect may be provided by oneor more physical components. In some forms, one physical component mayprovide one or more functional aspects. In use the seal-formingstructure 3100 is arranged to surround an entrance to the airways of thepatient so as to facilitate the supply of air at positive pressure tothe airways.

As shown in FIGS. 8A-9C, a patient interface 3000 in accordance with oneaspect of the present technology comprises the following functionalaspects: a seal-forming structure 3100, a plenum chamber 3200, apositioning and stabilising structure 3300, a vent 3400 and one form ofconnection port 3600 for connection to an air circuit (e.g. the aircircuit 4170 shown in FIGS. 1A-1C). In this example, the seal-formingstructure 3100 and the plenum chamber 3200 are provided by a cushionmodule 3150.

If a patient interface is unable to comfortably deliver a minimum levelof positive pressure to the airways, the patient interface may beunsuitable for respiratory pressure therapy.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 6 cmH₂O with respect to ambient.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 10 cmH₂O with respect to ambient.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 20 cmH₂O with respect to ambient.

5.3.1 Seal-Forming Structure

In one form of the present technology, a seal-forming structure 3100provides a target seal-forming region, and may additionally provide acushioning function. The target seal-forming region is a region on theseal-forming structure 3100 where sealing may occur. The region wheresealing actually occurs—the actual sealing surface—may change within agiven treatment session, from day to day, and from patient to patient,depending on a range of factors including for example, where the patientinterface was placed on the face, tension in the positioning andstabilising structure and the shape of a patient's face.

In one form the target seal-forming region is located on an outsidesurface of the seal-forming structure 3100.

In certain forms of the present technology, the seal-forming structure3100 is constructed from a biocompatible material, e.g. silicone rubber.

A seal-forming structure 3100 in accordance with the present technologymay be constructed from a soft, flexible, resilient material such assilicone.

In certain forms of the present technology, a system is providedcomprising more than one a seal-forming structure 3100, each beingconfigured to correspond to a different size and/or shape range. Forexample, the system may comprise one form of a seal-forming structure3100 suitable for a large sized head, but not a small sized head andanother suitable for a small sized head, but not a large sized head.

5.3.1.1 Sealing Mechanisms

In one form, the seal-forming structure 3100 includes a sealing flangeutilizing a pressure assisted sealing mechanism. In use, the sealingflange can readily respond to a system positive pressure in the interiorof the plenum chamber 3200 acting on its underside to urge it into tightsealing engagement with the face. The pressure assisted mechanism mayact in conjunction with elastic tension in the positioning andstabilising structure.

In one form, the seal-forming structure 3100 comprises a sealing flangeand a support flange. The sealing flange comprises a relatively thinmember with a thickness of less than about 1 mm, for example about 0.25mm to about 0.45 mm, which extends around the perimeter of the plenumchamber 3200. Support flange may be relatively thicker than the sealingflange. The support flange is disposed between the sealing flange andthe marginal edge of the plenum chamber 3200, and extends at least partof the way around the perimeter. The support flange is or includes aspring-like element and functions to support the sealing flange frombuckling in use.

In one form, the seal-forming structure may comprise a compressionsealing portion or a gasket sealing portion. In use the compressionsealing portion, or the gasket sealing portion is constructed andarranged to be in compression, e.g. as a result of elastic tension inthe positioning and stabilising structure.

In one form, the seal-forming structure comprises a tension portion. Inuse, the tension portion is held in tension, e.g. by adjacent regions ofthe sealing flange.

In one form, the seal-forming structure comprises a region having atacky or adhesive surface, and/or having a higher coefficient offriction compared to other surfaces.

In certain forms of the present technology, a seal-forming structure maycomprise one or more of a pressure-assisted sealing flange, acompression sealing portion, a gasket sealing portion, a tensionportion, and a portion having a tacky or adhesive surface.

5.3.1.2 Nose Bridge or Nose Ridge Region

In one form, the patient interface 3000 comprises a seal-formingstructure that forms a seal in use on a nose bridge region or on anose-ridge region of the patient's face.

In one form, the seal-forming structure includes a saddle-shaped regionconstructed to form a seal in use on a nose bridge region or on anose-ridge region of the patient's face.

5.3.1.3 Upper Lip Region

In one form, the patient interface 3000 comprises a seal-formingstructure that forms a seal in use on an upper lip region (that is, thelip superior) of the patient's face.

In one form, the seal-forming structure includes a saddle-shaped regionconstructed to form a seal in use on an upper lip region of thepatient's face.

5.3.1.4 Chin-Region

In one form the patient interface 3000 comprises a seal-formingstructure that forms a seal in use on a chin-region of the patient'sface.

In one form, the seal-forming structure includes a saddle-shaped regionconstructed to form a seal in use on a chin-region of the patient'sface.

5.3.1.5 Forehead Region

In one form, the seal-forming structure that forms a seal in use on aforehead region of the patient's face. In such a form, the plenumchamber may cover the eyes in use.

5.3.1.6 Nasal Pillows

In one form the seal-forming structure 3100 of the patient interface3000 comprises a pair of nasal puffs, or nasal pillows, each nasal puffor nasal pillow being constructed and arranged to form a seal with arespective naris of the nose of a patient. FIGS. 12A-F show a patientinterface 3000 having a seal-forming structure 3100 provided by apillows cushion module 3160. The pillows cushion module 3160 comprises apair of nasal pillows 3165. In this example, the same positioning andstabilising structure 3300 as shown in FIGS. 8A-9C is used to hold thepillows cushion module 3160 in sealing contact with the patient's nose.The same concepts and features of the positioning and stabilisingstructure 3300 described with reference to the cushion module 3150 maybe applied to a positioning and stabilising structure 3300 configured tobe used with the pillows cushion module 3160 (or another type of cushionmodule such as a full face cushion module, oro-nasal cushion module,ultra-compact full face cushion module, nasal cushion module and thelike).

Nasal pillows 3165 in accordance with an aspect of the presenttechnology include: a frusto-cone, at least a portion of which forms aseal on an underside of the patient's nose, a stalk, a flexible regionon the underside of the frusto-cone and connecting the frusto-cone tothe stalk. In addition, the structure to which the nasal pillow of thepresent technology is connected includes a flexible region adjacent thebase of the stalk. The flexible regions can act in concert to facilitatea universal joint structure that is accommodating of relative movementboth displacement and angular of the frusto-cone and the structure towhich the nasal pillow is connected. For example, the frusto-cone may beaxially displaced towards the structure to which the stalk is connected.

5.3.1.7 Nasal Cradle

In one form, for example as shown in FIGS. 8A-9C, the seal-formingstructure 3100 is configured to form a seal in use with the underside ofthe nose around the nares and optionally with the lip superior of thepatient 1000. This type of seal-forming structure may be referred to asa “cradle cushion” or “sub-nasal mask”. The shape of the seal-formingstructure may be configured to match or closely follow the underside ofthe patient's nose, i.e. the profile and angle of the seal-formingstructure may be substantially parallel to the patient's naso-labialangle. In one form of nasal cradle cushion, the seal-forming structurecomprises a bridge portion defining two orifices, each of which, in use,supplies air or breathable gas to a different one of the patient'snares. The bridge portion may be configured to contact or seal againstthe patient's columella in use. In some forms of the technology, theseal-forming structure 3100 is configured to form a seal on an undersideof the patient's nose without contacting a nasal bridge region of thepatient's nose. In some examples, patient interface may comprise aseal-forming structure 3100 in the form of a cradle cushion as describedin PCT Application No. PCT/AU2018/050289, filed Mar. 29, 2018, theentire contents of which are incorporated herein by reference.

5.3.1.8 Nasal Mask Cushion

In one form, the patient interface 3000 comprises a seal-forming portionthat forms a seal in use on an upper lip region (that is, the lipsuperior), a nasal bridge region and a cheek region of the patient'sface. This is the case, for example, with the patient interface 3000shown in FIG. 1B. This seal-forming portion delivers a supply of air orbreathable gas to both nares of patient 1000 through a single orifice.This type of seal-forming structure may be referred to as a “nasalcushion” or “nasal mask”. In some examples of the present technology,the positioning and stabilising structure 3300 shown in FIGS. 8A-9C maybe utilised to hold a nasal cushion in sealing position on a patient'sface.

5.3.1.9 Full-Face Mask Cushion

In one form the patient interface 3000 comprises a seal-forming portionthat forms a seal in use on a chin-region, a nasal bridge region and acheek region of the patient's face. This is the case, for example, withthe patient interface 3000 shown in FIG. 1C. This seal-forming portiondelivers a supply of air or breathable gas to both nares and mouth ofpatient 1000 through a single orifice. This type of seal-formingstructure may be referred to as a “full-face mask”. In some examples ofthe present technology, the positioning and stabilising structure 3300shown in FIGS. 8A-9C may be utilised to hold a full-face cushion insealing position on a patient's face.

5.3.1.10 Oronasal Mask Cushion

In another form the patient interface 3000 comprises a nasalseal-forming structure in the manner of a nasal cushion or nasal cradlecushion and an oral seal-forming structure that is configured to form aseal in use around the mouth of a patient (which may be referred to as a“mouth cushion” or “oral mask”). In such a mask air or breathable gas issupplied in use through separate orifices to the patient's nares and thepatient's mouth. This type of seal-forming structure 3100 may bereferred to as an “oronasal cushion” or “ultra-compact full facecushion”. In one form, the nasal seal-forming structure and oralseal-forming structure are integrally formed as a single component. Insome examples, patient interface may comprise a seal-forming structure3100 in the form of a cradle cushion as described in U.S. PatentApplication No. 62/649,376, the entire contents of which areincorporated herein by reference.

The plenum chamber 3200 has a perimeter that is shaped to becomplementary to the surface contour of the face of an average person inthe region where a seal will form in use. In use, a marginal edge of theplenum chamber 3200 is positioned in close proximity to an adjacentsurface of the face. Actual contact with the face is provided by theseal-forming structure 3100. The seal-forming structure 3100 may extendin use about the entire perimeter of the plenum chamber 3200. In someforms, the plenum chamber 3200 and the seal-forming structure 3100 areformed from a single homogeneous piece of material.

In certain forms of the present technology, such as in the patientinterface 3000 of FIGS. 8A-9C, the plenum chamber 3200 does not coverthe eyes of the patient in use. In other words, the eyes are outside thepressurised volume defined by the plenum chamber. Such forms tend to beless obtrusive and/or more comfortable for the wearer, which can improvecompliance with therapy.

In certain forms of the present technology, the plenum chamber 3200 isconstructed from a transparent material, e.g. a transparentpolycarbonate. The use of a transparent material can reduce theobtrusiveness of the patient interface, and help improve compliance withtherapy. The use of a transparent material can aid a clinician toobserve how the patient interface is located and functioning.

In certain forms of the present technology, the plenum chamber 3200 isconstructed from a translucent material. The use of a translucentmaterial can reduce the obtrusiveness of the patient interface, and helpimprove compliance with therapy.

5.3.2 Positioning and Stabilising Structure

The seal-forming structure 3100 of the patient interface 3000 of thepresent technology may be held in sealing position in use by thepositioning and stabilising structure 3300. Positioning and stabilisingstructure 3300 may be referred to as “headgear” since it engages thepatient's head in order to hold the patient interface 3000 in a sealingposition.

In one form the positioning and stabilising structure 3300 provides aretention force at least sufficient to overcome the effect of thepositive pressure in the plenum chamber 3200 to lift off the face.

In one form the positioning and stabilising structure 3300 provides aretention force to overcome the effect of the gravitational force on thepatient interface 3000.

In one form the positioning and stabilising structure 3300 provides aretention force as a safety margin to overcome the potential effect ofdisrupting forces on the patient interface 3000, such as from tube drag,or accidental interference with the patient interface.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured in a manner consistentwith being worn by a patient while sleeping. In one example thepositioning and stabilising structure 3300 has a low profile, orcross-sectional thickness, to reduce the perceived or actual bulk of theapparatus. In one example, the positioning and stabilising structure3300 comprises at least one strap having a rectangular cross-section. Inone example the positioning and stabilising structure 3300 comprises atleast one flat strap.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured so as not to be too largeand bulky to prevent the patient from lying in a supine sleepingposition with a back region of the patient's head on a pillow.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured so as not to be too largeand bulky to prevent the patient from lying in a side sleeping positionwith a side region of the patient's head on a pillow.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided with a decoupling portion located between ananterior portion of the positioning and stabilising structure 3300, anda posterior portion of the positioning and stabilising structure 3300.The decoupling portion does not resist compression and may be, e.g. aflexible or floppy strap. The decoupling portion is constructed andarranged so that when the patient lies with their head on a pillow, thepresence of the decoupling portion prevents a force on the posteriorportion from being transmitted along the positioning and stabilisingstructure 3300 and disrupting the seal.

In one form of the present technology, a positioning and stabilisingstructure 3300 comprises a strap 3310 constructed from a laminate of afabric patient-contacting layer, a foam inner layer and a fabric outerlayer. In one form, the foam is porous to allow moisture, (e.g., sweat),to pass through the strap 3310. The strap 3310 may be breathable toallow moisture vapour to be transmitted through the strap. In one form,the fabric outer layer comprises loop material to engage with a hookmaterial portion.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap that is extensible, e.g.resiliently extensible. For example the strap may be configured in useto be in tension, and to direct a force to draw a seal-forming structureinto sealing contact with a portion of a patient's face, in someexamples in combination with other straps or other structures. In anexample the strap may be configured as a tie.

A tie will be understood to be a structure designed to resist tension.In use, a tie is part of the positioning and stabilising structure 3300that is under tension. Some ties will impart an elastic force as aresult of this tension, as will be described. A tie may act to maintainthe seal-forming structure 3100 in a therapeutically effective positionon the patient's head.

In one form of the present technology, the positioning and stabilisingstructure comprises a first tie, the first tie being constructed andarranged so that in use at least a portion of an inferior edge thereofpasses superior to an otobasion superior of the patient's head andoverlays a portion of a parietal bone and/or frontal bone withoutoverlaying the occipital bone. The first tie may be provided, forexample, as part of a patient interface that comprises a cradle cushion,nasal pillows, nasal cushion, full-face cushion or an oronasal cushion.For example, as shown in FIGS. 8A-9C, the positioning and stabilisingstructure 3300 comprises a first tie in the form of tubes 3350 which lieover the top of the patient's head.

In one form of the present technology suitable for a nasal-only mask orfor a full-face mask, the positioning and stabilising structure 3300includes a second tie, the second tie being constructed and arranged sothat in use at least a portion of a superior edge thereof passesinferior to an otobasion inferior of the patient's head and overlays orlies inferior to the occipital bone of the patient's head. The secondtie may be provided, for example, as part of a patient interface thatcomprises a cradle cushion, nasal pillows, full-face cushion, nasalcushion or an oronasal cushion. As shown in FIGS. 8A-9C, the positioningand stabilising structure 3300 comprises a second tie in the form of astrap 3310 that lies against posterior surfaces of the patient's head.

In one form of the present technology suitable for a nasal-only mask orfor a full-face mask or oronasal mask, the positioning and stabilisingstructure 3300 includes a third tie that is configured to anchor againstposterior surfaces of the patient's neck. Additionally, in some formsthe positioning and stabilising structure comprises a fourth tie that isconstructed and arranged to interconnect the second tie and the thirdtie to reduce a tendency of the second tie and the third tie to moveapart from one another.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap that is bendable and e.g.non-rigid. An advantage of this aspect is that the strap is morecomfortable for a patient to lie upon while the patient is sleeping. Asshown in FIGS. 8A-9C, the positioning and stabilising structure 3300comprises a strap 3310 that is bendable. The strap 3310 may beconsidered a backstrap. The strap 3310 is sufficiently flexible to passaround the back of the patient's head and lie comfortably against thepatient's head, even when under tension in use.

In certain forms of the present technology, a system is providedcomprising more than one positioning and stabilizing structure 3300,each being configured to provide a retaining force to correspond to adifferent size and/or shape range. For example, the system may compriseone form of positioning and stabilizing structure 3300 suitable for alarge sized head, but not a small sized head, and another suitable for asmall sized head, but not a large sized head.

5.3.2.1 Headgear Tubing

In some forms of the present technology, the positioning and stabilisingstructure 3300 comprises one or more tubes 3350 that deliver pressurisedair received from a conduit forming part of the air circuit 4170 fromthe RPT device to the patient's airways, for example through the plenumchamber 3200 and seal-forming structure 3100. In the form of the presenttechnology illustrated in FIGS. 8A-9C, the positioning and stabilisingstructure 3300 comprises two tubes 3350 that deliver air to theseal-forming structure 3100 from the air circuit 4170. The tubes 3350are an integral part of the positioning and stabilising structure 3300of patient interface 3000 to position and stabilise the seal-formingstructure 3100 of the patient interface to the appropriate part of thepatient's face (for example, the nose and/or mouth). This allows theconduit of air circuit 4170 providing the flow of pressurised air toconnect to a connection port 3600 of the patient interface in a positionother than in front of the patient's face which may be unsightly to somepeople. While a pair of tubes 3350 have some advantages (describedbelow), in some examples, the positioning and stabilising structure 3300comprises only a single tube 3350 configured to overlie the patient'shead on one side. A strap or other stabilising component may be providedto the other side of the patient's head between the top end of thesingle tube 3350 and the seal-forming structure 3100, to providebalanced forces on the seal-forming structure 3100.

Since air can be contained and passed through headgear tubing 3350 inorder to deliver pressurised air from the air circuit 4170 to thepatient's airways, the positioning and stabilising structure 3300 may bedescribed as being inflatable. It will be understood that an inflatablepositioning and stabilising structure 3300 does not require allcomponents of the positioning and stabilising structure 3300 to beinflatable. For example, in the example shown in FIGS. 8A-9C and 12A-F,the positioning and stabilising structure 3300 comprises the headgeartubing 3350, which is inflatable, and the strap 3310, which is notinflatable.

In certain forms of the present technology, the patient interface 3000may comprise a connection port 3600 located proximal a top, side or rearportion of a patient's head. For example, in the form of the presenttechnology illustrated in FIGS. 8A-9C, the connection port 3600 islocated on top of the patient's head. In this example the patientinterface 3000 comprises an elbow 3610 to which the connection port 3600is provided. The elbow 3610 may swivel with respect to the positioningand stabilising structure 3300 and order to decouple movement of aconduit connected to the connection port 3600 from the positioning andstabilising structure 3300. Additionally, or alternatively, a conduitconnected to the connection port 3600 may swivel with respect to theelbow 3610. In the illustrated example, elbow 3610 comprises aswivelling conduit connector to which a conduit of the air circuit 4170is able to connect such that the conduit can rotate about itslongitudinal axis with respect to the elbow 3610. The connection port3600 may comprise fluid connection opening 3390, for example as shown inFIGS. 10A and 10B. In some examples the air circuit 4170 may connect tothe fluid connection opening 3390. The elbow 3610 may rotatably connectto the fluid connection opening or to a ring received in the fluidconnection opening.

Patient interfaces in which the connection port is not positioned infront of the patient's face may be advantageous as some patients find aconduit that connects to a patient interface in front of the face to beunsightly and obtrusive. For example, a conduit connecting to a patientinterface in front of the face may be prone to being tangled up inbedclothes or bed linen, particularly if the conduit extends downwardlyfrom the patient interface in use. Forms of the technology with apatient interface with a connection port positioned proximate the top ofthe patient's head in use may make it easier or more comfortable for apatient to lie or sleep in one or more of the following positions: in aside or lateral position; in a supine position (i.e. on their back,facing generally upwards); and in a prone position (i.e. on their front,facing generally downwards). Moreover, connecting a conduit to the frontof a patient interface may exacerbate a problem known as tube drag,wherein the conduit may provide an undesired drag force upon the patientinterface thereby causing dislodgement away from the face.

In the form of the present technology illustrated in FIGS. 8A-9C and12A-F, the positioning and stabilising structure 3300 comprises twotubes 3350, each tube 3350 being positioned in use on a different sideof the patient's head and extending across the respective cheek region,above the respective ear (superior to the otobasion superior on thepatient's head) to the elbow 3610 on top of the head of the patient1000. This form of technology may be advantageous because, if a patientsleeps with their head on its side and one of the tubes is compressed toblock or partially block the flow of gas along the tube, the other tuberemains open to supply pressurised gas to the patient. In other examplesof the technology, the patient interface 3000 may comprise a differentnumber of tubes, for example one tube, or three or more tubes. In oneexample in which the patient interface has one tube 3350, the singletube 3350 is positioned on one side of the patient's head in use (e.g.across one cheek region) and a strap forms part of the positioning andstabilising structure 3300 and is positioned on the other side of thepatient's head in use (e.g. across the other region) to assist insecuring the patient interface 3000 on the patient's head.

In the form of the technology shown in FIGS. 8A-9C and 12A-F the twotubes 3350 are fluidly connected at their upper ends to each other andto connection port 3600. In one embodiment, the two tubes are integrallyformed while in other embodiments the tubes are separate components thatare connected together in use and may be disconnected, for example forcleaning or storage. Where separate tubes are used they may beindirectly connected together, for example each may be connected to aT-shaped conduit having two conduit arms each fluidly connectable to thetubes 3350 and a third conduit arm or opening acting as the connectionport 3600 and connectable in use to the air circuit 4170. The connectionport 3600 may comprise an elbow 3610 received in fluid connectionopening 3390 at the centre of two integrally formed tubes 3350. Theelbow 3610 may be received in a ring in the fluid connection opening3390 and may be configured to swivel within the ring. The fluidconnection opening 3390 may be also considered a connection port 3600itself.

The tubes 3350 may be formed of a semi-rigid material such as anelastomeric material, e.g. silicone. For example, the tubes 3350, fromthe left-side non-extendable tube section 3363 to the right sidenon-extendable tube section 3363, may be formed (e.g., by molding) froma single homogeneous piece of material, such as silicone, as can be seenin FIG. 10A. The tubes may have a natural, preformed shape and be ableto be bent or moved into another shape if a force is applied to thetubes. For example, the tubes may be generally arcuate or curved in ashape approximating the contours of a patient's head between the top ofthe head and the nasal or oral region.

The positioning and stabilising structure 3300 in some examples maycomprise sleeves 3364 around the tubes 3350. For example, as shown inFIGS. 8A to 8D, sleeves 3364 are provided to the non-extendable tubesections 3363. In some examples, the patient interface 3000 may notcomprise sleeves 3364 and in other examples the patient interface 3000may comprise sleeves 3364 that cover more, or all, of the tubes 3350.The sleeves 3364 may be formed to fit to the curved shape of the tubes3350. In some examples, the sleeves 3364 are formed from a smoothfabric. The sleeves 3364 may be more comfortable against the patient'sface than the tube 3350 without any covering.

As described in U.S. Pat. No. 6,044,844, the contents of which areincorporated herein, the tubes 3350 may be crush resistant to avoid theflow of breathable gas through the tubes if either is crushed duringuse, for example if it is squashed between a patient's face and pillow.Crush resistant tubes may not be necessary in all cases as thepressurised gas in the tubes may act as a splint to prevent or at leastrestrict crushing of the tubes 3350 during use. A crush resistant tubemay be advantageous where only a single tube 3350 is present as if thesingle tube becomes blocked during use the flow of gas would berestricted and therapy will stop or reduce in efficacy.

In certain forms of the technology, one or more portions of the tubes3350 may be rigidised by one or more rigidising or stiffening elements.Examples of rigidising elements include: sections of the tubes 3350 thatare comparatively thicker than other sections; sections of the tubes3350 that are formed from a material that is comparatively more rigidthat the material forming other sections; and a rigid member attached tothe inside, outside or embedded in a section of tube. The use of suchrigidising elements helps to control how the positioning and stabilisingstructure 3300 will function in use, for example where the tubes 3350 ismore likely to deform if forces are applied to them and where the shapeof the tubes 3350 is more likely to be maintained if forces are applied.The selection of where such rigidising elements are positioned in thetubes 3350 can therefore help to promote comfort when the patientinterface 3000 is worn and can help to maintain a good seal at theseal-forming structure 3100 during use. Rigidising or stiffeningelements may be in positioning and stabilising structures 3300 which areconfigured to support relatively heavy seal-forming structures such asfull face or oro-nasal cushion assemblies.

The tubes 3350 in the form of the technology shown in FIGS. 8A-9C and12A-F have a length of between 15 and 30 cm each, for example between 20and 27 cm each. In one example each of the tubes are around 26 cm long.In another example each of the tubes is around 23 cm long. The length ofthe tubes is selected to be appropriate for the dimensions of the headsof typical patients, for example the distance between the regionproximate the top of the head where the upper end of the tubes 3350 aresituated, and the region proximate the openings to the patient's airwaysat which the lower end of the tubes 3350 connect to the cushion module3150 (or pillows cushion module 3160) when following a generally arcuatepath down the sides of the heads and across the patient's cheek regionsuch as is shown in FIG. 8A-9C or 12A-F. As described in more detailbelow, the patient interface 3000 is configured so that the length ofthe tubes 3350 can be varied in some forms of the technology and theabove lengths may apply to the tube in a contracted, stretched orneutral state. It will be appreciated that the length of the tubes 3350will depend on the length of other components in the patient interface3000, for example the length of arms of a T-shaped conduit to which theupper ends of tubes 3350 connect and/or the size of the plenum chamber3200.

5.3.2.1.1 Positioning of Headgear Components

Each tube 3350 may be configured to receive a flow of air from theconnection port 3600 on top of the patient's head and to deliver theflow of air to the seal-forming structure at the entrance of thepatient's airways. In the example of FIGS. 8A-9C and 12A-F, the at leastone tube 3350 extends between the seal-forming structure 3100 and theconnection port 3600 across the patient's cheek region and above thepatient's ear, i.e. a portion of tube 3350 that connects to the cushionmodule overlays a maxilla region of the patient's head in use and aportion of tube 3350 overlays a region of the patient's head superior tothe otobasion superior on the patient's head. Each of the one or moretubes 3350 may also lie over the patient's sphenoid bone and/or temporalbone and either or both of the patient's frontal bone and parietal bone.The connection port 3600 and elbow 3610 may be located in use over thepatient's parietal bone, frontal bone or the junction therebetween.

The exemplary form of the technology illustrated in FIGS. 8A-9C and12A-F has tubes 3350 which curve around the upper part of the patient'shead from the upper end of the tubes 3350 that connect to elbow 3610 ontop of the head to the point at which the strap 3310 connects to thetubes 3350 with relatively little curvature in the sagittal plane. Inbetween the point at which the strap 3310 connects to the tubes 3350 andthe lower ends of the tubes 3350 at which they connect with the cushionmodule 3150 in front of the patient's airways under the nose, the tubes3350 curve forwards between the patient's ears and eyes and across thecheek region. The radius of curvature of this section of the tubes 3350may be in the range 60-100 mm, for example 70-90 mm, for example 80 mm.The lower end of the tubes 3350 and the section of the tubes 3350 atwhich the strap 3310 connects to the tubes 3350 may subtend an angle inthe range 65-90°, for example 75-80°. The actual curvature present inthe portions of the tubes 3350 superior to the strap 3310, and theactual curvature in the portions of the tubes 3350 inferior to the strap3310, depends on patient setup and in practice will vary depending onthe shape and size of the patient's head and the patient's preferences.

The degree to which the patient interface 3000 fits an individualpatient can be altered by varying the length of the tubes 3350 and,alternatively or additionally, by altering the position of the patientinterface 3000 or portions thereof on the patient's head. For example, apatient interface 3000 having tubes 3350 of a certain length can beadjusted to better fit a patient by moving portions of the positioningand stabilising structure 3300 in the posterior or anterior direction onthe patient's head. For example, positioning the junction of the tubes3350 above the patient's head further forward (i.e. in the anteriordirection) enables a patient interface 3000 having tubes 3350 of acertain length to fit a larger head than if the junction of the tubes3350 is positioned further backward (i.e. in the posterior direction).In most patient, if the junction of the tubes 3350 is positionedforwardly, the superior portions of the tubes 3350 lie over a smallerportion of the patient's head than if the junction of the tube 3350 ispositioned rearwardly.

In certain forms of the present technology the patient interface 3000 isconfigured such that the connection port 3600 can be positioned in arange of positions across the top of the patient's head so that thepatient interface 3000 can be positioned as appropriate for the comfortor fit of an individual patient. One way this can be achieved so thatthe seal-forming structure 3100 forms an effective seal with thepatient's face irrespective of the position of the connection port 3600on the patient's head is to de-couple movement of the upper portion ofthe patient interface 3000 from the lower portion of the patientinterface 3000. Such de-coupling can be achieved using, for example,mechanisms that allow parts of the gas delivery tubes 3350 to easilymove or flex relative to other parts of the patient interface 3000. Suchmechanisms will be described below.

In a certain form of the present technology, the patient interface 3000is configured such that the connection port 3600 is positionedapproximately at a top point of the patient's head. The connection port3600 may be positioned in the sagittal plane and aligned with theotobasion superior points in a plane parallel to the coronal plane. Theotobasion superior points are identified in FIG. 2D. As will bedescribed below, in some forms of the technology, the positioning andstabilising structure 3300 is configured to be worn in differentpositions, with the effect that the connection port 3600 may bepositioned proximate the top of the patient's head in the sagittal planeup to around 20 mm forward or 20 mm rearward of the otobasion superiorpoints.

In some examples of the present technology, the connection port 3600 maybe positioned in the sagittal plane and aligned with a junction betweenthe frontal bone and the parietal bones. The connection port 3600 may bepositioned approximately over the junction of the coronal suture and thesagittal suture. In this configuration, the superior portions of thetubes 3350 may lie over and/or along a portion of the coronal suture.However, as mentioned above the patient has the ability to move theconnection port 3600 anteriorly or posteriorly in order to adjust thefit of the patient interface 3000.

An advantage provided by the tubes 3350 overlying the patient's headslightly anterior to the superior-most point (e.g. at or proximate thecoronal suture) is that the risk of the tubes 3350 riding in a posteriordirection in use may be reduced. In many patients there may be a recessor “divot” where the coronal suture meets the sagittal suture. Thepositioning and stabilising structure 3300 may be particularly stablewhen tubes 3350 lie within this divot. Accordingly, in some examples thetubes 3350 are configured with appropriate curvature and/or ability tocurve in order to lie over the coronal suture.

As described above, in some examples of the present technology thepatient interface 3000 comprises a seal-forming structure 3100 in theform of a cradle cushion which lies generally under the nose and sealsto an inferior periphery of the nose. The positioning and stabilisingstructure 3300 may be structured and arranged to pull the seal-formingstructure 3100 into the patient's face under the nose with a sealingforce vector that has a posterior and superior direction (e.g. aposterosuperior direction). A sealing force vector with aposterosuperior direction may facilitate the seal-forming structure 3100forming a good seal to both the inferior periphery of the patient's noseand the anterior-facing surfaces of the patient's face on either side ofthe patient's nose and the upper lip.

In some examples, the positioning and stabilising structure 3300 may inuse apply a sealing force vector having a posterosuperior direction atan angle of approximately 35° with respect to the patient's Frankforthorizontal. The superior portions of the tubes 3350 (e.g. the portionsof the tubes 3350 superior to the strap 3310) may be orientedvertically, and the strap 3310 may extend from the tubes 3350 in aposteroinferior direction at an angle of approximately 35° with respectto the patient's Frankfort horizontal. In this particular setup, thereis an angle of 125° formed between the strap 3310 and the superiorportions of the tubes 3350 where the strap 3310 connects to the tubes3350.

FIG. 8D shows a side view of a patient wearing the patient interface3000. Certain forces acting on a point 3308 above each of the patient'sears proximate where the strap 3310 connects to the tubes 3350 areidentified in FIG. 8D. The superior portions of the tubes 3350 may applya vertical force 3301 on the point 3308 resulting from headgear tension.The force 3301 may have a substantially vertical direction. The inferiorportions of the tubes 3350 (e.g., between the seal-forming structure3100 and the connection to the strap 3310) may apply an anteroinferiorforce 3303 on this point 3308 in an anterior inferior direction at anangle of approximately 125° to the vertical force 3301 applied by thesuperior portions of the tubes 3350. The anteroinferior force 3303 maybe equal in magnitude and opposite in direction to the sealing force atwhich the seal-forming structure 3100 is pulled into the patient's faceunder the nose. To balance the forces, the strap 3310 applies aposteroinferior force 3302 in a posteroinferior direction at an angle ofapproximately 125° to the vertical force 3301 applied by the superiorportions of the tubes 3350. Accordingly, there is an angle ofapproximately 110° between the anteroinferior force 3303 applied to thepoint 3308 along each tube 3350 above the patient's ear and theposteroinferior force 3302 applied by the strap 3310.

A sealing force vector of 35° may be considered optimal for manypatients when the positioning and stabilising structure 3300 is usedwith a cradle cushion. Additionally, the directions of the forcesdescribed above applied by each portion of the positioning andstabilising structure 3300 may be considered ideal. However, it will beappreciated that that, in practice, the actual directions of the forcesapplied by each portion of the headgear will vary to accommodate theparticular anatomy and preferences of each patient.

For example, in many examples the positioning and stabilising structure3300 may be configured such that the superior portions of the tubes 3350lie across the patient's head slightly anterior to a superior-mostpoint. For some patients this may result in the tubes 3350 being angledslightly anteriorly rather than aligned vertically (e.g. in the coronalplane) in order to lie within a slight recess at or proximate thecoronal suture of the skull. In such an example, the tension in thestrap 3310 could be adjusted by the patient to balance the forces andachieve the optimal sealing force vector.

In some examples, the positioning and stabilising structure 3300 may beconfigured to apply a force on the seal-forming structure 3100 in aposterosuperior direction at an angle that bisects an angle formedbetween the upper lip and the columella (e.g. the surfaces forming thenasolabial angle).

In certain examples of the present technology, the tubes 3350 areconfigured to receive the strap 3310 at the locations superior to andproximate the patient's ears. If the strap 3310 connects to the tubes3350 to high with respect to the patient's head, the strap 3310 may havea tendency to ride up the back of the patient's head. Additionally, thestrap 3310 could form too large of an angle with respect to the superiorportions of the headgear tubes 3350, resulting in the necessity for thepatient to tighten the strap 3310 excessively, which could result inboth excessive tension in the positioning and stabilising structure 3300and make the strap 3310 more likely to ride up the back of the patient'shead. Accordingly, it is advantageous for the connection between thestrap 3310 and the tubes 3350 to be provided as low as possible butspaced from the top of the patient's ear sufficiently that upontightening of the strap 3310, the tubes 3350 are not pulled into contactwith the patient's ears.

5.3.2.1.2 Headgear Tube Fluid Connections

The two tubes 3350 are fluidly connected at their inferior ends to theplenum chamber 3200. In the examples of FIGS. 8A-9C and 12A-F, the tubes3350 form a fluid connection with the cushion module 3150 andseal-forming structure 3100. In certain forms of the technology, theconnection between the tubes 3350 and the cushion module 3150 isachieved by connection of two rigid components so that the patient caneasily connect the two components together in a reliable manner. Thetactile feedback of a ‘re-assuring click’ or like sound may be easy fora patient to use or for a patient to know that the tube has beencorrectly connected to the cushion module 3150. In one form, the tubes3350 are formed from silicone and the lower end of each of the siliconetubes 3350 is overmolded to a rigid connector made, for example, frompolypropylene, polycarbonate, nylon or the like. The rigid connector maycomprise a male mating feature configured to connect to a female matingfeature on the cushion module 3150. Alternatively, the rigid connectormay comprise a female mating feature configured to connect to a malemating feature on the cushion module 3150. The same manner of connectionby which the tubes 3350 are connected to the cushion module 3150 mayalso be applied to the connection between the tubes 3350 and the cushionmodule 3150, or another plenum chamber 3200 or seal-forming structure3100.

In another embodiment a compression seal is used to connect each tube3350 to the cushion module 3150. For example, a resiliently flexible(e.g. silicone) tube 3350 without the rigid connector may need to besqueezed slightly to reduce its diameter so that it can be jammed into aport in the plenum chamber 3200 and the inherent resilience of thesilicone pushes the tube 3350 outwards to seal the tube 3350 in the portin an air-tight manner. In a hard-to-hard type engagement between thetube 3350 and port, a pressure activated seal such as a peripheralsealing flange may be used. When pressurised gas is supplied through thetubes 3350 the sealing flange is urged against the join between thetubes and the inner circumferential surface of the port of the plenumchamber 3200 to enhance the seal between them. If the port is soft and arigid connector is provided to the tube 3350, the pressure activatedseal as described earlier may also be used to ensure the connection isair-tight. In another example, each tube 3350 is formed from aresiliently flexible (e.g. silicone) material which is over moulded to arigid connector such that the resiliently flexible material fits overthe rigid connector and itself functions as a gasket to seal theconnection between the tube 3350 and the cushion module 3150 around aperiphery of an air flow passage from the tube 3350 into the plenumchamber 3200 of the cushion module 3150.

Similar connection mechanisms may be used to fluidly connect the tubes3350 with a T-shaped top member defining the connection port 3600 orconnectable to the connection port 3600 in some forms of the technology.In one embodiment, a swivel elbow connected at the connection port 3600is rotatable in order to drive a port size adjustment mechanism thatdecreases or increases the size of the ports into which tubes 3350 areinserted in order to improve the fit of the tubes through an increase ordecrease of compressive forces and to reduce unintended leakage.

5.3.2.1.3 Extendable Concertina Structure

The patient interface 3000 may comprise one or more extendable tubesections. In some examples, an extendable tube section comprises anextendable concertina structure 3362. The patient interface 3000 maycomprise a positioning and stabilising structure 3300 including at leastone gas delivery tube comprising a tube wall 3352 having an extendableconcertina structure 3362. For example, the patient interface 3000 shownin FIGS. 8A-9C and 12A-F comprises tubes 3350, the superior portions ofwhich comprise extendable tube sections each in the form of anextendable concertina structure 3362.

Each extendable concertina structure 3362 may comprise a portion of thetube 3350 having one or more folding portions, pleats, corrugations orbellows to form an extendable portion of the tube 3350. In the exampleshown in FIGS. 8A-9C, the extendable concertina structures 3362 eachtake the form of an extendable concertina structure. The extendableconcertina structures 3362 are separated by the elbow 3610 andconnection port 3600. The extendable concertina structures 3362 are ableto change in length. In particular, each extendable concertina structure3362 is able to extend or contract in order to change the length of therespective tube 3350.

In some examples, each gas delivery tube 3350 at the extendableconcertina structure 3362 may comprise a cross-section having a widthand a height, where the width is larger than the height and is alignedin use substantially with the anterior-posterior directions. Forexample, the patient interface 3000 illustrated in FIGS. 8A-8C comprisesextendable concertina structures 3362 each having a cross-sectionalwidth greater than a cross-sectional height, the width being thedimension aligned with the anterior and posterior directions of theillustrated patient 1000. In this example, the width is about twice aslarge as the height. That said, in this example the width reduces alongthe length of the extendable concertina structure 3362. At a superior,or medial, end of each extendable concertina structure 3362, the widthof the tube wall forming the extendable concertina structure 3362 isrelatively larger and is a similar size to a ring in which the swivelelbow 3610 is received in the tube 3350. At an inferior, or lateral, endof each extendable concertina structure 3362, the width of the tube wallis relatively smaller and is a similar size to the width of thenon-extendable tube section 3363. An extendable concertina structure3362 that changes in width between the larger tube size of theconnection to the elbow 3610 and the smaller tube size of thenon-extendable tube sections 3363 may provide for a sleek and contiguoustube 3350 that may be more comfortable and/or aesthetically appealing(which may improve patient compliance with therapy).

5.3.2.1.3.1 Bendability

In some examples of the present technology, portions of the positioningand stabilising structure 3300 are configured to be more resistant tobending in or about some directions or axes than in or about others.

For example, a superior portion of each tube 3350 of the positioning andstabilising structure 3300 shown in FIGS. 8A-9C may be more bendable ina particular direction in comparison to an orthogonal direction. Eachgas delivery tube 3350 of the positioning and stabilising structure 3300may comprise a superior tube portion 3304 configured to overlie asuperior region of the patient's head in use (as illustrated in FIGS.8A-C). In the illustrated example, the superior tube portion 3304includes the extendable concertina structure 3362. In other examples ofthe present technology, the superior tube portion 3304 may comprise analternative extendable tube structure (such as one of the optionsdisclosed in PCT Patent Publication No. WO 2017/124155, the entirecontents of which are incorporated herein by reference) or may benon-extendable.

The superior tube portion 3304 comprises a first end 3305 and a secondend 3306. In this example the first end 3305 is configured to overlie orlie against a superior portion of the patient's head, at approximatelysagittal plane of the patient's head (e.g. approximately top and centreof the patient's head). The second end 3306 is configured to overlie thepatient's head laterally from the first end 3305 (e.g. closer to theside of the patient's head). In some examples, if the superior tubeportion 3304 is not particularly long, the second end 3306 may lielaterally with respect to the first end 3305 but may not lieparticularly inferior to the first end 3305. In other examples, if thesuperior tube portion 3304 is longer, the second end 3306 may lie bothlaterally and inferiorly to the first end 3305. FIG. 13 shows a portionof another example of a positioning and stabilising structure 3300. Thepositioning and stabilising structures of FIGS. 8A-9C and also FIG. 13are able to bend about multiple axes. For example, the positioning andstabilising structure 3300 in FIG. 13 is able to drape down over thepatient's head and also curve in the anterior and posterior directions.As illustrated in FIG. 13, the superior tube portion 3304 is bent abouttwo axes.

The superior tube portion 3304 may also comprise one or more stiffenedportions between the first end 3305 and the second end 3306. Thestiffened portion(s) may be configured to provide a higher resistance torelative movement between the first end 3305 and a second end 3306 in ananterior and/or posterior direction than in a superior and/or inferiordirection.

When the patient dons the positioning and stabilising structure 3300,the superior tube portion 3304 may have a relatively low resistance tobending in the vertical directions such that the second end 3306 is ableto move inferiorly with respect to the first end 3305. Thisadvantageously enables the superior tube portion 3304 to “drape”downwardly over the top of the patient's head to the side of thepatient's head. A relatively high degree of bendability and thesuperior/inferior directions may be advantageous in enabling thesuperior tube portion 3304 to conform to the curvature of the patient'shead.

Additionally, the superior tube portion 3304 may have a relativelyhigher resistance to bending in the horizontal directions such that thefirst end 3305 does not unintentionally move anteriorly and/orposteriorly with respect to the second end 3306. This advantageouslyenables the superior tube portion 3304 to remain in a desired positionacross the top of the patient's head. With a lower resistance to bendingtowards the anterior and/or posterior directions, the superior tubeportion 3304, and in particular the connection port 3600, may be lesslikely to ride forward or backward along the top of the patient's headin use. This resistance to a forward or backward movement of thesuperior tube portion 3304 is particularly advantageous for the patientinterface 3000 given the connection to the air circuit 4170 is providedatop the patient's head, meaning tube drag forces may act directly onthe superior tube portion 3304.

In some examples, the superior tube portion 3304 may comprise a shapewhich inherently provides the advantageous resistance to bending. Forexample, the superior tube portion 3304 may comprise a rectangularcross-section one of the parallel long sides configured to lie againstthe surfaces of the patient's head. The long sides of the rectangularcross section provide a relatively large resistance to bending of thesuperior tube portion in directions parallel to the long sides (e.g. theanterior and/or posterior directions in use). However, the short sidesof the rectangular cross section may not provide such a large resistanceto bending of the superior tube portion 3304 and directions parallel tothe short sides (e.g. the inferior and/or superior directions in use).It will be appreciated that the cross-section of the superior tubeportion 3304 may not be perfectly rectangular. For example, the cornersand/or short sides may be rounded.

The stiffened portion may be formed by one or more rigidising structuresformed by or provided to the tube wall of the tube 3350. In the examplesshown in FIGS. 8A-10J, the stiffened portion is formed by a plurality ofridge connecting portions 3370 that are configured to resist separationof adjacent ridges formed by folds in the tube wall. In particular, thestiffened portion is formed by a series of ridge connecting portions3370 along both the anterior side of the superior tube portion 3304 andthe posterior side of the superior tube portion 3304. A tube 3350 thatcomprises stiffened portions on both the anterior and posterior sides ofthe tube 3350 may advantageously have a higher resistance to bendingtowards both the anterior and posterior sides of the tube 3350. However,in some examples a stiffened portion is provided to only one of theanterior or posterior sides of the tube 3350 since, depending on thestiffness, a stiffened portion on one side only may provide a sufficientresistance to bending towards both directions.

In some examples the stiffened portion of a tube 3350 may be provided toan extendable portion of the superior tube portion 3304. In the exampleillustrated in FIGS. 8A-10J, the extendable portion comprises anextendable concertina structure 3362 formed in a tube wall of the tube3350, the extendable concertina structure 3362 comprising a plurality ofridges 3372 and a plurality of grooves 3373, as will be described inmore detail below. In this example, the stiffened portion comprises aplurality of ridge connecting portions 3370 formed in the tube wall,each of the plurality of ridge connecting portions 3370 connecting apair of adjacent ridges 3372. The stiffening effects of the ridgeconnecting portions 3370 are described in more detail below.

In other examples of the present technology, the patient interface 3000may comprise tubes 3350 having stiffened portions formed by structuresother than ridge connecting portions. In some examples, portions of thetubes 3350 (e.g. anterior and/or posterior portions) may comprisestiffened portions being stiffened with one or more rigidising elements.The tubes 3350 may be rigidised with one or more rigidising componentshaving a higher stiffness than the tube 3350 embedded within the tubewall. For example, the tube wall may be overmoulded to an elongate baror rod formed from a material stiffer than the tube wall. In otherexamples, a stiffened portion of the tube wall may be provided byfurther features of the geometry of the tube wall. In one example thetube wall may comprise a greater material thickness at the anteriorand/or posterior sides of the tube 3350. In another example, the tubewall may comprise a reduced groove depth (or ridge height) at stiffenedportions of the tubes 3350.

5.3.2.1.3.2 Ridges and Grooves

The extendable concertina structure 3362 forming each extendable tubesection comprises a plurality of ridges 3372 and a plurality of grooves3373, as shown in FIGS. 10D-10J. The ridges 3372 and grooves 3373 arealternatingly formed into the wall of each tube 3350 to form aconcertina structure. An alternating series of ridges and grooves willbe understood to refer to a series in which a groove is provided betweeneach pair of ridges and a ridge is provided between each pair of grooves(e.g. ridge, groove, ridge, groove and so on).

The alternating ridges 3372 and grooves 3373 may function like folds orbellows able to fold and unfold independently or in concert to shortenor lengthen the extendable concertina structure 3362 and hence therespective tube 3350. A large groove depth (or ridge height) may providefor a more extendable tube 3350. When tension is applied to the tubes3350, the ridges 3372 and grooves 3373 of the extendable concertinastructures 3362 may be pulled away from each other which straightens outthe tube wall, lengthening the tubes 3350. In this example, theextendable concertina structure 3362 is biased to an original (e.g.unextended) length. Upon release of headgear tension the ridges 3372 andgrooves 3373 are biased back to an original configuration in which eachextendable concertina structure 3362 and the tubes 3350 have originallengths.

In addition to facilitating a change in the length, the ridges 3372 andgrooves 3373 may also facilitate a change in shape of the extendableconcertina structure 3362 of each tube 3350. In some examples of thepresent technology, a first series of alternating ridges 3372 andgrooves 3373 is provided to a first side of the tube 3350 in theextendable concertina structure 3362 (e.g. a patient-contacting side),while a second series of alternating ridges 3372 and grooves 3373 isprovided to a second, opposite, side of the tube 3350 (e.g. anon-patient-contacting side). The extendable concertina structure 3362may facilitate bending of the tube 3350 as the ridges 3372 and grooves3373 are able to move with respect to each other by differing degrees onthe different sides of the tube 3350. For example, on the first side ofthe tube 3350 the ridges 3372 and grooves 3373 may contract while on thesecond side of the tube 3350 the ridges 3372 and grooves 3373 mayexpand, with the result being that the tube 3350 bends in the extendableconcertina structure 3362. Alternatively, the ridges 3372 and grooves3373 on both the first side and the second side may expand, in use, butthe ridges 3372 and groove 3373 on the first side may expand less toenable to tube 3350 to bend (e.g. curve) in the direction of the firstside, for example to conform or wrap to (e.g. drape over) the patient'shead while extending in length.

In some examples, the first alternating series of ridges 3372 andgrooves 3373 may have a lesser extension stiffness (e.g. a lesser forcerequired to achieve a change in unit length) than the second alternatingseries of ridges 3372 and grooves 3373. The reduced extension stiffnessin the non-patient-contacting side of the extendable concertinastructure 3362 may advantageously facilitate bending/curvature in thetubes 3350 in use by enabling the outboard side of the tube 3350 toextend to cover a greater arc length then the inboard side of the tubes3350 in the extendable concertina structure 3362. While the extensionstiffness of both the first and the second alternating series of ridges3372 and grooves 3373 may differ from one another, the extensionstiffnesses of each may be selected to achieve a desired overallextension stiffness of the extendable concertina structure 3362.

The ridges 3372 and grooves 3373 may each be formed along a portion ofthe tube wall around a majority of a longitudinal axis of the tube 3350,such as on all, or almost all, of the sides of the tube 3350. This mayenable the extendable concertina structure 3362 to bend about multipleaxes. As shown in FIGS. 10H-10J and FIG. 13, extendable concertinastructures 3362 according to examples of the present technology mayenable the tubes 3350 in multiple axes. FIGS. 10H and 10I show anextendable concertina structure 3362 bending in the superior-inferiordirections (e.g. to drape over a patient's head), FIG. 10J shows theextendable concertina structure 3362 bending in the anterior-posteriordirections (e.g. to enable the tubes 3350 to lie over the top of thepatient's head at different locations) and FIG. 13 shows an extendableconcertina structure 10J bending in both the superior-inferior andanterior-posterior directions at the same time.

In some examples, each of the ridges 3372 and grooves 3373 aresubstantially straight. In other examples, the ridges 3372 and/orgrooves 3373 may comprise one or more arcuate portions.

As shown in FIG. 10D, each ridge 3372 comprises a central curved ridgeportion 3374. That is, each ridge 3372 comprises an accurate portion inthe centre thereof. However, at the ends of each ridge 3372 are straightridge portions 3375. Accordingly, each of the ridges 3372 comprises apair of straight ridge portions 3375 provided at opposite ends of theridge 3372.

Similarly, each groove 3373 comprises a curved groove portion 3376central the respective groove. The centre of each groove 3373 istherefore accurate. Additionally, at the end of each groove 3373 is astraight groove portion 3377. Each of the grooves 3373 comprises a pairof straight groove portions 3377 provided at opposite ends of the groove3373. Each of the curved groove portions 3376 may comprise curvaturematching or defined by the curvature of the pair of adjacent ridges3372, in particular the curvature of the curved ridge portions 3374.

Each of the ridge connecting portions 3370 connects a respectiveadjacent pair of ridges 3372 at the straight ridge portions 3375 of thepair of ridges 3372. The straight groove portions 3377 may each bedefined between adjacent straight ridge portions 3375 on either sidealong the length of the tube 3350 and a ridge connecting portion 3370either superior or inferior to the straight groove portion 3377 (as thecase may be for each straight groove portion 3377, depending on whetherit is on a superior or inferior side of the tube 3350).

While the extendable concertina structure 3362 comprises ridges 3372 andgrooves 3373 on an exterior of the gas delivery tube 3350, the foldsforming the extendable concertina structure 3362 may also form ridgesand grooves interior to the gas delivery tube 3350 (e.g. as a result ofthe folds forming a wavelike shape in the tube wall, such as asinusoidal shape, square wave or other waveform). FIG. 10B shows theparticular wavelike shape formed in the tube walls. As shown in FIG.10B, the extendable concertina structure 3362 comprises folds forminginterior ridges 3382 and interior grooves 3383. In particular, the foldsin the tube wall form, interior to the tubes 3350, a first alternatingseries of interior ridges 3382 a and interior grooves 3383 a along thenon-patient-contacting side of the tube 3350. Additionally, the foldsform a second alternating series of interior ridges 3382 b and interiorgrooves 3383 b along the patient-contacting side of the tubes 3350.

Each interior groove 3383 a of the first alternating series may beprovided opposite a respective interior groove 3383 b of the secondalternating series across the interior of the tube 3350 to form aplurality of opposing groove pairs. That is, each interior groove 3383 aon the non-patient-contacting side of the tube 3350 may be paired withan opposing interior groove 3383 b on the patient-contacting side. Asillustrated in FIG. 10B, each opposing groove pair comprises a firstinterior groove 3383 a and a second interior groove 3383 b. In thisexample, the first interior groove 3383 a comprises a greater groovedepth than the second interior groove 3383 b. The greater groove depthof the first interior groove 3383 a in each opposing groove pair resultsin the first alternating series of ridges and grooves having a lowerextension stiffness than the second alternating series. In otherexamples of the present technology, the relatively lower stiffness ofthe ridges and grooves forming the first alternating series may beprovided by stiffening the second alternating series of ridges andgrooves. In one example, ridge connecting portions 3370 (describedseparately below) are provided to the tube wall to connect pairs ofadjacent ridges. In another example, the second alternating series ofridges and grooves are formed by a stiffer material than the firstalternating series (e.g. a different material having a higher stiffnessor, in the case of the tube being formed from silicone, a region ofsilicone having a higher Durometer, etc.). In a further example, thesecond alternating series of ridges and grooves may be stiffened with arigidising component.

In the illustrated example, the tube wall of the tube 3350 comprises agreater material thickness at a base of the second interior groove 3383b of each opposing groove pair than at a base of the first interiorgroove 3383 a of the respective groove pair. The greater materialthickness forming the basis of the second interior groove 3383 b of eachof those in groove pair reduces the groove depth of the second interiorgroove 3383 b. The reduced groove depth reduces the extendibility of theextendable concertina structure 3362 on the side having the secondalternating series of ridges and grooves.

As shown in FIG. 10B, the material thickness of the tube wall at thebase of each interior groove 3383 b of the second alternating seriesreduces along the length of the tube 3350 from the first end proximatethe connection port 3600 to a second end. Additionally, the materialthickness of the tube wall at the base of each interior groove 3383 a ofthe first alternating series is substantially constant along the lengthof the tube 3350. The groove depth of the interior grooves 3383 a and3383 b of the first and second alternating series of interior ridges3382 and interior grooves 3383 reduces along the length of the gasdelivery tube 3350 from the first end adjacent the connection port 3600to the second end. The reduction in groove depth on both sides of thetube 3350 along the length of the extendable concertina structure 3362facilitate a change in size of the tube 3350 between the largerconnection port 3600 and the smaller non-extendable tube section 3363.While the groove depth is generally lesser at the second end incomparison to the first end, for each opposing groove pair, the secondinterior groove 3383 b on the second, patient-contacting side, of theextendable concertina structure 3362 has a lesser groove depth then theopposing first interior groove 3383 a on the first,non-patient-contacting side.

In this example, the first interior groove 3383 a of each opposed groovepair is joined to the second interior groove 3383 b of the respectiveopposed groove pair at sides of the tube 3350 between thenon-patient-contacting side and the patient-contacting side. That is,tube 3350 is grooved all of the way around the interior of the tubewall. The first interior groove 3383 a and second interior groove 3383 bof each opposed groove pair are therefore contiguous. Similarly, eachinterior ridge 3382 a of the first alternating series of interior ridges3382 a and interior grooves 3383 a contiguous with an opposing interiorridge 3382 b of the second alternating series interior ridges 3382 b andinterior grooves 3383 b.

5.3.2.1.3.3 Ridge Connecting Portions

As shown in FIGS. 10D-10J, the extendable concertina structures 3362also comprise a plurality of ridge connecting portions 3370 provided tothe tube wall of the gas delivery tube 3350. Each of the ridgeconnecting portions 3370 connects a pair of adjacent ridges 3372. Theridge connection portions 3370 may each comprise an integrally formedportion of the tube wall. Each ridge connection portion 3370 may beformed into the tube wall. Each ridge connection portion 3370 connectstwo or more adjacent ridges 3372 and is configured to resist separationof the ridges 3372. The ridge connection portions 3370 may not preventseparation of the ridges 3372 but may increase the stiffness of theextendable concertina structure 3362.

One function of the ridge connecting portions 3370 is to reduce theability of the extendable concertina structures 3362 to extend. Whilethe extendable concertina structures 3362 are intended to extend, andthere are be advantages associated with tubes 3350 that are extendablein length, an excessively extendable tube 3350 may be difficult for apatient to use comfortably and securely. The ridge connecting portions3370 therefore temper the ability of the extendable concertina structure3362 to increase in length but do not prevent it from extending at all.In the illustrated example, the ridge connecting portions 3370 incombination with the ridges 3372 and grooves 3373 form extendableconcertina structures 3362 that facilitate sufficient extension to thelengths of the tubes 3350 to improve the ability of the positioning andstabilising structure 3300 to fit to a range of patient head sizeswithout being so flexible that sufficient tension and sealing forcecannot be achieved.

Each pair of adjacent ridges 3372 of an extendable concertina structure3362 may be connected by at least one ridge connecting portion 3370.Alternatively, or additionally, one or more pairs of adjacent ridges3372 may be connected by two ridge connecting portions 3370. As shown inFIGS. 10D-10J, each pair of adjacent ridges 3372 of the extendableconcertina structure 3362 is connected by two ridge connecting portions3370. Each of the ridge connecting portions 3370 may be spaced centrallybetween an inferior side of the gas delivery tube 3350 (e.g. a patientcontacting side) and a superior side of the gas delivery tube 3350 (e.g.an upwardly and/or outwardly facing side).

Another function of the ridge connecting portions 3370 is that theyprovide localised stiffening to the extendable concertina structures3362. Localised stiffening provided to the extendable concertinastructure 3362 may be advantageous for headgear tubes 3350 that areintended to easily bend about one axis while having a particularresistance to bending about a different axis.

In some examples, ridge connecting portions 3370 are provided betweenridges 3372 and grooves 3373 on sides of the tube 3350 configured tobend less than other sides of the tube 3350. One or more ridgeconnecting portions 3370 may be located on an anterior-facing side ofthe gas delivery tube 3350. Alternatively, or additionally, one or moreridge connecting portions 3370 may be located on a posterior-facing sideof the gas delivery tube 3350.

In the illustrated example, as shown in FIGS. 10D-10J, ridge connectingportions 3370 are provided to the positioning and stabilising structure3300 between ridges 3372 on the anterior and posterior sides of theextendable concertina structures 3362. That is, each pair of adjacentridges 3372 is connected by a ridge connecting portion 3370 located onthe anterior-facing side of the gas delivery tube 3350. Additionally,each pair of adjacent ridges 3372 is connected by a ridge connectingportion 3370 located on the posterior-facing side of the gas deliverytube 3350.

Since the ridge connecting portions 3370 are located on the anterior andposterior sides in this example, the ridge connecting portions 3370provide greater resistance to the extendable concertina structures 3362bending towards the anterior and posterior directions than towards thesuperior and inferior directions. This is advantageous since theextendable concertina structures 3362 maintain the ability to bend tofit to the superior and lateral surfaces of the patient's head. Thisability to bend results in the tubes 3350 being able to drape down overthe patient's head and fit comfortably. Meanwhile, the reduced abilityof the extendable concertina structure 3362 to bend towards the anteriorand posterior directions may reduce the tendency of the superior-mostportion of the positioning and stabilising structure 3300 to move orride anteriorly or posteriorly in use, which may compromise stability ofthe patient interface 3000.

The provision of ridge connecting portions 3370 may be advantageous inlimiting the extendibility of the extendable concertina structures 3362without excessively compromising the ability of the extendableconcertina structures 3362 to bend about particular axes in which it isadvantageous for the extendable tube sections to do so.

Another function provided by the ridge connecting portions 3370 in someexamples of the present technology is added resistance to twisting ofthe extendable concertina structures 3362. As the connection port 3600is provided between the extendable concertina structures 3362, tube dragforces in some circumstances could act on the tubes 3350 to inducetwisting in the extendable concertina structures 3362. The low-profileshape of the tubes 3350 (e.g. the approximately rectangular crosssection) may provide resistance to twisting, however the ridgeconnecting portions 3370 advantageously provide further twistingresistance. The ridge connecting portions 3370 may stiffen the anteriorand posterior sides of the extendable concertina structures 3362,functioning as stiffening portions, to reduce the possibility of thetubes 3350 twisting.

In some examples of the present technology, the grooves 3373 of anextendable concertina structure 3362 may be formed as depressions withrespect to outer surfaces of the gas delivery tube 3350. In otherexamples, the ridges 3372 of the extendable concertina structure 3362may be raised with respect to outwardly facing surfaces of the tube walland the grooves 3373 may be formed by the spaces between the raisedridges 3372. As shown in FIGS. 10D-10J, the grooves 3373 are formed asdepressions with respect to outer surfaces of the tube 3350. The outersurfaces of the tube 3350 from which the grooves 3373 recessed may becontiguous with an outer surface of the non-extendable tube section3363. An advantage of forming the grooves 3373 as depressions withrespect to an outer surface of the tubes 3350 is that the ridges 3372 donot protrude outwardly from beyond the outer surface of thenon-extendable tube section 3363. Outwardly protruding ridges may beuncomfortable for the patient.

Also as shown in FIGS. 10D-10J, outwardly facing surfaces of the ridgeconnecting portions 3370 do not protrude outwardly with respect to alongitudinal axis of the tube further than the ridges 3372.Additionally, each of the ridge connecting portions 3370 comprises anoutwardly facing surface contiguous with outwardly facing surfaces ofadjacent ridges 3372. It may be less aesthetically pleasing for theridge connecting portions 3370 to protrude outwardly with respect to thelongitudinal axis of the tube 3350 further than the ridges 3372,although they may do so in some examples of the present technology, forexample to provide increased bending and/or twisting resistance.

Furthermore, as shown in FIGS. 10D-10J, each of the plurality of grooves3373 is located between a respective pair of ridge connecting portions3370. Each respective ridge connecting portion 3370 is located at arespective end of a respective groove 3373. Additionally, each of theplurality of grooves 3373 comprises a groove depth and each of theplurality of ridge connecting portions 3370 comprises a ridge connectingportion height. For each respective set of ridge connecting portions3370 and grooves 3373, the groove depth is equal to the ridge connectingportion height. That is, the groove depth of each groove 3373 is equalto the ridge connection portion height of each ridge connecting portion3370 of the respective pair of ridge connecting portions 3370 located atthe end of the respective groove 3373. Accordingly, the grooves 3373 areformed as depressions with respect to outer surfaces of the ridgeconnection portions 3370, ridges 3372 and tube wall of the tube 3350.

The ridge connection portions 3370 may be relatively narrow andrib-like, as shown in the illustrated example. Alternatively, the ridgeconnection portions 3370 may be thicker (e.g. such that they occupy alarger portion of the anterior and posterior sides of the extendableportions of the tubes 3350).

In the illustrated examples, the ridge connecting portions 3370 areprovided on an exterior side of the tubes 3350. That is, the ridgeconnecting portions 3370 connect ridges 3372 on the outside of the tubewall, rather than on the inside which defines the hollow interior withinthe tubes 3350. In other examples, the ridge connecting portions 3370may be provided to an interior side of the tube wall of the tubes 3350.The folds in the tube wall forming the extendable concertina structure3362 may form, on an interior side of the tube wall, a series ofalternating ridges and grooves inverse to the series of ridges 3372 andgrooves 3373 formed on the exterior side of the tube wall. That is, thefolds forming a ridge 3372 on the exterior of the tube wall may form agroove around an interior of the tube wall. Similarly, the folds forminga groove 3373 on the exterior of the tube wall may form a ridge on theinterior of the tube wall.

Ridge connecting portions 3370 may connect between adjacent ridges oneither the exterior or the interior of the tube 3350 to resistseparation of the ridges. In an example of a positioning and stabilisingstructure 3300 with ridge connecting portions 3370 on the exterior ofthe tube 3350, the ridges 3372 on the exterior of the tube are connectedand would require greater tension to be separated, while the ridges onthe interior of the tube would be more freely separable. Similarly, inan alternatively example of a positioning and stabilising structure 3300with ridge connecting portions 3370 connecting ridges on the interior ofthe tube 3350, the ridges on the interior of the tube wall require agreater force to be separated, while the ridges on the exterior of thetube are more freely separable. In some examples, ridge connectionportions 3370 connect a combination of interior and exterior rides.

In some examples of the present technology, a single ridge connectionportion 3370 connects multiple ridges 3372. In other examples, eachridge connection portion 3370 connects only a single pair of adjacentridges 3372. In some examples, one or more ridge connection portions3370 may connect non-adjacent ridges 3372 (e.g. first and last ridges,every second ridge, etc.).

5.3.2.1.4 Non-Extendable Headgear Tubing

The patient interface 3000 may comprise one or more non-extendable tubesections 3363. For example, the patient interface 3000 shown in FIGS.8A-9C comprises tubes 3350, the inferior portions of which comprisenon-extendable tube sections 3363. The non-extendable tube sections 3363are configured to overlie the patient's cheeks and may be configured tocontact the patient's face inferior to the patient's cheekbones. Eachnon-extendable tube section 3363 may lie on a curve extending inferiorlyfrom the connection between the respective headgear tube 3350 and thenextending in a partially anterior and partially medial direction towardsthe seal-forming structure 3100 in order to avoid the patient's cheekbones.

It is advantageous that the positioning and stabilising structure to3300 of the patient interface 3000 does not lie over the patient's cheekbones. The regions of a patient's face inferior to the cheekbones aregenerally more fleshy and a patient may find it more tolerable for theheadgear tubes 3350 to lie over these regions of the face. Additionally,since the cheek bone regions of the patient's face are relatively unableto move or deform, the non-extendable tube sections 3363 lie firmlyagainst the fleshy cheek regions. Further, the patient's cheek bones canassist in preventing the inferior portions of the headgear tubes 3350from riding up over the cheekbones towards the patient's eyes. When thenon-extendable tube sections 3363 fit snugly against the patient'scheeks below the cheekbones, the hardness and prominence of thepatient's cheekbones may provide a barrier to the headgear tubes 3350riding up towards the patient's eyes (which could affect stabilityand/or may obscure the patient's vision).

The cross-sectional shape of the non-extendable tube sections 3363 ofthe tubes 3350 may be circular, elliptical, oval, D-shaped or a roundedrectangle, for example as described in U.S. Pat. No. 6,044,844. Across-sectional shape that presents a flattened surface of tube on theside that faces and contacts the patient's face or other part of thehead may be more comfortable to wear than, for example a tube with acircular cross-section.

The cross-sectional width and/or height of the tubes 3350 may be in therange 8-25 mm, for example 10-20 mm. In some forms in which the tubeshave a D-shaped cross-section, for example in the case of thelongitudinal section of headgear tubing 3350 shown in FIG. 10C, thetubes have a width in the range 15-25 mm, for example 20 mm, and aheight in the range 8-15 mm, for example 10 mm. The height may beconsidered to be the dimension of the tube extending away from thepatient's face in use, i.e. the distance between the patient contactingside 3348 and the outermost part of the non-patient contacting side3349, while the width may be considered to be the dimension across thesurface of the patient's head. The cross-sectional thickness of thematerial forming the tubes 3350 may be in the range 0.8-1.6 mm, forexample 1.0-1.5 mm, for example 1.3 mm.

The D-shaped cross-sectional tube 3350 has rounded edges 3347 flankingthe patient contacting side 3348. Rounded edges in contact with, orproximate to, the patient's skin help the patient interface 3000 to bemore comfortable to wear and to avoid leaving marks on, or irritating,the patient's skin. A tube with a D-shaped cross-sectional profile isalso more resistant to buckling than other shaped profiles.

A further advantage of the D-shaped cross section of the non-extendabletube sections 3363 of the tubes 3350 is that the non-extendable tubesections 3363 that lie in front of the patient's face in use are moreresistant to bending in the vertical directions than in the horizontaldirections. The D-shaped cross-section makes the non-extendable tubesections 3363 more resistant to bending parallel to the long axis of theD-shape than to bending perpendicular to the long axis of the D-shape.This is advantageous as the non-extendable tube sections 3363 are morereadily able to bend to curve inwardly around the front of the patient'sface to the seal-forming structure 3100, yet retain stiffness and thevertical direction to enable the vertical forces applied on thenon-extendable tube section 3363 from the extendable concertinastructure 3362 to be transferred to the seal-forming structure 3100 inorder to provide the necessary sealing force to the seal-formingstructure 3100.

The ability to bend inwardly around the front of the patient's faceenables the non-extendable tube section 3363 to fit snugly against thepatient's cheeks inferior to the patient's cheekbones. As describedabove in more detail, non-extendable tube sections 3363 that lie snuglyunder the patient's cheekbones may provide for a more stable seal thannon-extendable tube sections 3363 that lie loosely over the patient'scheeks or lie high over the patient's cheekbones.

In other examples, the non-extendable tube sections 3363 may comprise arectangular shaped cross-section. A rectangular cross-section mayprovide similar advantages to a D-shaped cross-section. In particular, arectangular cross-section may provide the non-extendable tube section3363 with a greater resistance to bending in a direction parallel to theshort sides of the rectangular cross section. In other examples, thenon-extendable tube sections 3363 may comprise an elliptical oroval-shaped cross-section which would provide similar advantages.

In some examples of the present technology, the non-extendable tubesections 3363 connect to a cushion module 3150 from a low angle. Asdescribed above, the headgear tubes 3350 may extend and inferiorly downthe sides of the patient's head and then curve anteriorly and mediallyto connect to a cushion module 3150 in front of the patient's face. Thetubes 3350, before connecting to the cushion module 3150, may extend toa location at the same vertical position as or, in some examples,inferior to the connection with the cushion module 3150. That is, thetubes 3350 may project in an at least partially superior directionbefore connecting with the cushion module 3150. A portion of the tubes3350 may be located inferior to the cushion module 3150 and/or theseal-forming structure 3100. The low position of the tubes 3350 in frontof the patient's face facilitates contact with the patient's face belowthe patient's cheekbones.

5.3.2.2 Headgear Sizing and Stiffness

Positioning and stabilising structures 3300 may vary in size betweendifferent examples of the present technology. Providing different sizeoptions for the patient interface 3000 may enable more patients to beaccommodated. A loop around the patient's head may be formed by the pairof headgear tubes 3350 and the cushion module 3150 (or the pillowscushion module 3160 or other seal-forming structure 3100) connectedbetween the inferior ends of the tubes 3350. The size of this loop maybe varied in order to provide for different size patient interfaces3000.

In one example, the unextended length of the loop formed by the tubes3350 and the cushion module 3150, measured along the centreline of thepatient-facing side of the loop, may be within the range of 510-610 mm.In some examples, the unextended length of this loop may be within therange of 525-600 mm. In some examples the length of this loop may bewithin the range of 535-590 mm.

In some particular examples, the unextended length of the loop referredto above may be within the range of 528-548 mm, such as within the rangeof 535-541 mm, for example about 538 mm. In further particular examples,the length of this loop may be within the range of 534-554 mm, such aswithin the range of 539-549 mm, such as about 544 mm or about 547 mm, inexamples. In further particular examples, the unextended length of thisloop may be within the range of 541-561 mm, such as within the range of546-556 mm, for example about 551 mm.

In other particular examples, the unextended length of the loop referredto above may be within the range of 564-584 mm, such as within the rangeof 571-581 mm, such as about 574 or about 579 mm, in examples. Infurther examples, the unextended length of this loop may be within therange of 577-597 mm, such as within the range of 582-592 mm, such asabout 583 mm or about 587 mm, in examples.

The length of the gas delivery tubes 3350, in particular, may be variedin order to provide different sizes of the positioning and stabilisingstructure 3300. In some examples, the unextended length of the tubes3350 measured along the centreline of the patient-facing side of thetubes 3350 may be within the range of 500-535 mm, such as between510-525 mm, such as within the range of 512-522 mm, for example about517 mm. In further examples, the unextended length of the tubes 3350 maybe within the range of 460-500 mm, such as between 470-490 mm, such aswithin the range of 475-485 mm, for example about 481 mm.

As described in more detail above, in some examples of the presenttechnology, the headgear tubes 3350 comprise extendable portions (e.g.extendable concertina structures 3362). In some examples of the presenttechnology, the extendable portion of a gas delivery tube 3350 (e.g. asingle concertina portion on one side of the positioning and stabilisingstructure 3300) may comprise a stiffness (for extension) within a rangeof 2-3.5N/10 mm (e.g. 0.2-0.35 N/mm). In particular examples, theextendable portion may comprise a stiffness within a range of 2.5-3N/10mm (e.g. 0.25-0.3 N/mm). In one example, the extendable portion maycomprise a stiffness of approximately 2.75N/10 mm (e.g. 0.275 N/mm). Infurther examples of the present technology, the extendable portion of atube 3350 may require between 2.5N and 3N of tension to extend in lengthby 10 mm and may require between 5N and 5.5N of tension to extend inlength by 20 mm. It will be appreciated that, in various examples ofpatient interfaces 3000 according to the present technology, any ofthese disclosed stiffnesses may be provided to tubes 3350 having any ofthe sizes (e.g. lengths) described above.

5.3.2.3 Headgear Straps

In certain forms of the present technology, the positioning andstabilising structure 3300 comprises at least one headgear strap actingin addition to the tubes 3350 to position and stabilise the seal-formingstructure 3100 in sealing position at the entrance to the patient'sairways. As shown in FIGS. 8A-9C, the patient interface 3000 comprises astrap 3310 forming part of the positioning and stabilising structure3300. The strap 3310 may be known as a back strap or a rear headgearstrap, for example. In other examples of the present technology, one ormore further straps may be provided. For example, a patient interface3000 according to an example of the present technology having a fullface or oro-nasal cushion module may have a second, lower, strapconfigured to overlie the back of the patient's neck.

5.3.2.3.1 Strap

In the example shown in FIGS. 8A-9C, strap 3310 of the positioning andstabilising structure 3300 is connected between the two tubes 3350positioned on each side of the patient's head and passing around theback of the patient's head, for example overlying or lying inferior tothe occipital bone of the patient's head in use. The strap 3310 connectsto each tube above the patient's ears. In other embodiments, for exampleas part of an oro-nasal patient interface, the positioning andstabilising structure 3300 comprises an upper strap similar to strap3310 and at least one additional lower headgear strap that connectsbetween the tubes and/or cushion module and passes below the patient'sears and around the back of the patient's head. Such a lower headgearstrap may also be connected to an upper strap (e.g. a similar to strap3310).

In certain forms of the technology, the positioning and stabilisingstructure 3300 comprises a mechanism for connecting a headgear strap tothe headgear tubes 3350. The headgear strap may be connected directly orindirectly to the headgear tubes 3350. In the case of the patientinterface 3000 shown in FIGS. 8A-9C, for example, a tab 3320 configuredto connect to strap 3310 projects outwardly from each headgear tube 3350in a generally posterior direction. The tabs 3320 have holes in them toreceive the ends of strap 3310.

In some forms of the present technology, the strap 3310 is adjustable.For example, in the case of the patient interface shown in FIGS. 8A-9Cthe strap 3310 is, in use, threaded through a hole in the form of aneyelet in each tab 3320. The length of the strap 3310 between the tabs3320 may be adjusted by pulling more or less of the strap 3310 throughone or both of the tabs 3320. The strap 3310 may be secured to itselfafter passing through the eyelets in the tabs 3320, for example, withhook-and-loop fastening means. The strap 3310 therefore is able to beadjusted to fit around different head sizes. In some forms of thetechnology the angle of the strap 3310 relative to the headgear tubes3350 or patient's head is able to be adjusted to fit around thepatient's head at different locations. This adjustability assists thepositioning and stabilising structure 3300 to accommodate different headshapes and sizes.

In some forms of the technology, the strap 3310 exerts a force on theheadgear tubes 3350 to pull them in an at least partially posterior(e.g. rearwards) direction at the locations of the tabs 3320. The strap3310 may also exert a force on the headgear tubes 3350 to pull them inan at least partially inferior (e.g. downwards) direction. The magnitudeof this force may be adjusted by altering the length of the strap 3310between the tabs 3320.

In some forms of the technology, such as the example shown in FIG.8A-9C, the direction of the force applied to the headgear tubes 3350 bythe strap 3310 may also be altered. This direction may be altered byadjusting the angle of the strap 3310 relative to the headgear tubes3350 or patient's head. In some forms of the technology the location atwhich the strap 3310 exerts a force on the headgear tubes 3350 may bealtered by adjusting the location at which the strap 3310 is secured tothe headgear tubes 3350.

The adjustability of the magnitude and direction of the force applied tothe headgear tubes 3350 by the strap 3310 may advantageously enable thepositioning and stabilising structure 3300 to accommodate a range ofhead sizes and head shapes. The strap 3310 may balance forces in theheadgear tubes 3350 which may assist the headgear to maintain its shapeand an effective seal to the patient's face, while remainingcomfortable.

In some forms of the technology, when worn by a patient, a point on theheadgear tubes 3350 near the tab 3320 will receive a generally upward(e.g. superior) force from the upper portion of the headgear tubes 3350due to tension in the headgear tubes 3350 and, in some examples, due toa biasing mechanism (described in further detail below) acting to keepthe headgear secured to the patient's head. Additionally, the point onthe headgear tubes 3350 near the tab 3320 may receive a generallyforward (e.g. anterior) and downward (e.g. inferior) force caused by abiasing mechanism acting to urge the seal-forming structure 3100 upwardsand into the patient's nose. The directions and magnitudes of the forcesrequired for a secure fit and effective seal may vary between patientsbased on the position of the positioning and stabilising structure 3300on the head, which may vary due to, for example, differences in headshapes and sizes. In some forms of the technology, the adjustability ofthe strap 3310 enables the forces to be balanced for a range of headshapes and sizes to hold the positioning and stabilising structure 3300in a comfortable position while maintaining an effective seal.

For example, to provide a larger force acting in the posterior (e.g.rearward) direction on the portions of the headgear tubes 3350 proximatethe tabs 3320, the strap 3310 may be adjusted by pulling more of thestrap 3310 through the slots in the tabs 3320. Doing so will cause thestrap 3310 to shorten in length and, especially if the strap 3310 iselastic, to apply a larger force on the headgear tubes 3350 in theposterior (e.g. rearward) direction. Similarly, the angle of the strap3310 may be adjusted as required to balance both the vertical andhorizontal components of the forces acting on the portions of theheadgear tubes 3350 proximate the tabs 3320, across a range of headshapes and sizes.

The strap 3310 may comprise a rectangular cross-section along some orall of its length. Additionally, the strap 3310 may have a profile withone or more rounded edges to provide greater comfort and to reduce therisk of headgear straps marking or irritating the patient. In certainforms of the present technology, a positioning and stabilising structure3300 comprises a strap 3310 that is bendable and e.g. non-rigid. Anadvantage of this aspect is that the strap 3310 is more comfortable fora patient to lie upon while the patient is sleeping.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap 3310 that comprises two ormore strap bands separated by a split. For example, as shown in FIGS.8A-9C and 12A-F, the strap 3310 comprises a split 3313 configured in useto be located against the posterior of the patient's head. A strap 3310may anchor the patient interface 3000 on the patient's head in aparticularly stable fashion in the case of some patient interfacedesigns. The posterior of the patient's head may have complex geometryand the presence of a split 3313 in the strap 3310 may assist the strapto better conform to the back of the patient's head.

5.3.2.3.2 Eyelets

As noted above, each of the gas delivery tubes may comprise an eyeletfor connection with a strap. In some examples, the eyelet may becircular. In other examples, the eyelets may be elongate. Alternatively,the eyelets may have a round side and a straight side. The eyelets maybe D-shaped, for example. The eyelets in the exemplary patient interface3000 shown in FIGS. 8A-9C are in the form of slits 3322. In thisexample, the pair of gas delivery tubes 3350 provide a pair of slits3322 to which a strap 3310 is able to be connected. That is, the strap3310 may connect between the eyelets. The strap 3310 may be constructedand arranged to contact, in use, a region of the patient's head inferiorto or overlaying an occipital bone of the patient's head. In thisexample, the slits 3322 are formed in tabs 3320 connected to the tubewalls of the tubes 3350.

In some examples of the present technology, the eyelets may be locatedon each tube 3350 each between 70 mm and 150 mm along the tube 3350 fromthe centre of the pair of tubes 3350 (e.g. the connection port 3600). Infurther examples, each eyelet may be located between about 110 mm and130 mm along each tube 3350 from the centre of the pair of tubes 3350.In particular examples the eyelets may be located between around 120 mmand 125 mm along each tube 3350 from the connection port 3600. In thecase of the illustrated positioning and stabilising structure 3300,having slits 3322, the midpoints of the slits are located around 120-125mm from the centre of the pair of gas delivery tubes 3350.

The exemplary patient interface 3000 shown in FIGS. 8A-9C includes asingle strap 3310 passing between the slits 3322 and which willtypically need to apply a force on the tubes 3350 in a partiallyinferior and partially posterior direction. To apply a force on thetubes 3350 in the necessary direction, the strap 3310 should wrap lowaround the back of the patient's head. Typically, the back of thepatient's head will generally curve inferiorly and anteriorly over theoccipital bone of the skull towards where the head joins the patient'sneck.

If the strap 3310 does not lie low enough around the back of thepatient's head (e.g. not inferior to the posterior-most point of thepatient's head, where the posterior surfaces of the patient's head curvetowards the anterior direction and faith partially in an inferiordirection) there is a risk that the strap 3310 may ride up the back ofthe patient's head in use. If the strap 3310 rides up superior to theposterior-most point of the patient's head, the strap 3310 may lie on aregion of the patient's head that faces in a partially superiordirection. If this occurs, it is possible that tension in the strap 3310could pull the strap up further, which could result in failure of thepositioning and stabilising structure 3300 to provide the necessarysealing force vector to the seal-forming structure 3100 (after which theseal to the patient's face could be compromised and the patient wouldneed to re-don the patient interface 3000).

As illustrated in FIGS. 11A-11C, each of the gas delivery tubes 3350 maycomprise a tube wall 3352 defining a hollow interior along the length ofthe tube 3350 (e.g. forming a conduit). The pressurised flow of air isable to travel from the connection port 3600, through the hollowinterior within the tube wall 3352 for delivery to the seal-formingstructure 3100.

In the example illustrated in FIGS. 11A-11C, the tube 3350 comprises atab 3320. In this example the tabs 3320 of the positioning andstabilising structure 3300 are each integrally formed with a respectivetube wall 3352 of the tubes 3350. Alternatively, the tabs 3320 may beseparate parts assembled with the tube 3350. For example, the tabs 3320may comprise separate components that movably connect to the tubes 3350to enable adjustment of the position and/or angle of the tabs 3320.Integrally forming the tabs 3320 with the tube walls 3352 may improvethe usability of the positioning and stabilising structure 3300 byreducing the assembly required. Additionally, integrally formed tabs3320 may enable a seamless connection between tabs 3320 and tube walls3352, reducing the possibility of the connection causing discomfort tothe patient.

In the illustrated example, each of the tubes 3350 comprises anextendable tube section in the form of an extendable concertinastructure 3362. Each tab 3320 is joined to the tube wall 3352 of the gasdelivery tube 3350 inferior to the extendable tube section. Inparticular, each tab 3320 is joined to the tube wall 3352 of the gasdelivery tube 3350 at a non-extendable tube section 3363 inferior to theextendable tube section. In some examples the tabs 3320 may each have asuperior edge 3331 spaced along the length of the tube 3350 from an endof the extendable tube section. In other examples the tabs 3320 may havesuperior edges 3331 which meet the tube wall 3352 at or proximate aninferior end of the extendable tube section.

In the examples illustrated in FIGS. 11A-11C, the slits 3322 of thetubes 3350 are formed in the tabs 3320. In other examples, slits 3322may be formed directly into the tube wall 3352 or may be formed intoanother portion of the positioning and stabilising structure 3300 or aseparate component configured to connect to the positioning andstabilising structure 3300.

The slits 3322 may each be spaced posteriorly in use from the tube wallof the respective tube 3350. In particular, each slit 3322 may be spacedposteriorly from slit-adjacent portion 3355 of the tube wall 3352alongside the respective slit 3322. The slit-adjacent portion 3355 ofthe tube wall 3352 may be the portion of the tube wall 3352 to which thetab 3320 is connected. More particularly, the slit-adjacent portion 3355of the tube wall 3352 may be the portion of the tube wall 3352 that ismost adjacent to the slit 3322. In some examples, the slit 3322 may bespaced posteriorly with respect to the entire length of the tube wall3352. The slit 3322 may be located superior to the otobasion superior ofthe patient's head in use.

In the manner illustrated in FIGS. 8A-8C, each of the tube walls 3352are configured to overlie the patient's head along a path 3353 passingbetween an eye and an ear of the patient. A portion of the path 3353 isillustrated in FIGS. 11A and 11B. In some examples, the path 3353 isgenerally the path on the surfaces of the patient's head over and alongwhich the tube walls 3350 lie. Additionally, the path 3353 may be thepath along which gas flowing through the tubes 3350 travels from the topof the patient's head to the seal-forming structure 3100. In practice,the path 3353 may comprise a curve in three-dimensional space (e.g. aspace curve), since in some examples the path 3353 may not be confinedto a plane. In the illustrated examples, the tubes 3350 track laterallyand inferiorly over the sides of the patient's head and then inferiorly,anteriorly and medially to connect with the cushion module 3150.

As illustrated in FIGS. 11A-11C, each of the slits 3322 comprises asuperior end 3326 and an inferior end 3327. The superior end 3326 andinferior end 3327 may also be considered first and second ends,respectively. In this example, the superior end 3326 is spaced furtherfrom the slit-adjacent portion 3355 of the tube wall 3352 than theinferior end 3327. As shown in FIG. 11A, the superior end 3326 of theslit 3322 is spaced from the tube wall 3352 by a spacing identified withSE in the illustration. The inferior and 3327 of the slit 3322 is spacedfrom the tube wall 3352 by a spacing identified with IE. As illustrated,the spacing SE is larger than the spacing IE and, accordingly, thesuperior end 3326 is spaced further from the tube wall 3352 than theinferior end 3327. When a patient has donned a patient interface 3000including the positioning and stabilising structure 3300, the superiorend 3326 is spaced posteriorly with respect to the inferior end 3327.Unless the context clearly requires otherwise, if an end of a slit oreyelet is described as being spaced further from a tube wall thananother end of the slit or eyelet, the spacing referred to is to beunderstood to be with respect to a generally adjacent or closest portionof the tube wall to the slit or eyelet (e.g. a slit-adjacent oreyelet-adjacent portion).

As illustrated in FIG. 11B, the slit 3322 is oriented at an angle withrespect to the orientation of the tube 3350 at a slit-adjacent portion3355 of the tube wall 3352. The slit 3322 is also oriented at an anglewith respect to the path 3353 at the slit-adjacent portion 3355 of thetube wall 3352. In this example, the slit 3322 is arcuate between thesuperior end 3326 and the inferior end 3327. The slits 3322 each have acurved elongate shape. In other examples, each slit 3322 may be straightbetween the superior end 3326 and the inferior end 3327. The curved,arcuate shape of the slits 3322 may advantageously enable a strap 3310passing through the slit to centre within the slit 3322 and may alsoallow the slit 3322 to tolerate some variation in the angle of the strap3310 passing through the slit 3322, without causing the strap 3310 tobunch up towards one end of the slit 3322.

Illustrated in FIG. 11B is a length axis 3323 of the slit 3322. Thelength axis 3323 in this example is defined along the general length ofthe slit 3322 as the slit is elongate. A slit 3322 that is arcuate inshape, such as the slit 3322 shown in FIGS. 11A-C may still comprise alength axis as it is elongate. It will be appreciated that in the caseof the slit 3322, the length axis 3323 may not be parallel with everyportion of the sides of the slit 3322 but may be defined by the generaldirection from one end of the slit 3322 to the other. Alternatively, thelength axis 3323 of the slit 3322 may be defined by a tangent to thecurvature of the slit 3322 at a central portion of the slit 3322.

The slit 3322 may have a posterosuperior-anteroinferior orientation inuse. That is, the length of the slit 3322 (e.g. the length axis 3323)may be aligned parallel to a line extending between a posterosuperiordirection and an anteroinferior direction. With this orientation, thesuperior end 3326 of the slit 3322 is spaced posteriorly with respect tothe inferior end 3327 of the slit 3322. Illustrated in FIG. 11B is atangent 3354 to the path 3353 at the slit-adjacent portion 3355 of thetube 3350. As shown, the length axis 3323 of the slit 3322 forms a slitangle 3321 with the tangent 3354 of the path 3353. In this example, theslit angle 3321 is an oblique angle. The oblique angle may be in therange of 5 to 30 degrees. In some examples, the oblique angle may bewithin the range of 10 to 20 degrees. For example, the oblique angle maybe within the range of 12 to 18 degrees. In specific examples, theoblique angle may be about 13 degrees, 15 degrees or 17 degrees. In someexamples, the slit 3322 may angled with respect to a longitudinal axisalong the length of the extendable concertina structure 3362. Inparticular, the slit 3322 may be oriented at an angle of between 15 and45 degrees with respect to a longitudinal axis of the extendableconcertina structure 3362 when straightened. For example, this angle maybe within the range of 20 and 40 degrees, such as within the range of 22and 35 degrees. In particular examples, the angle may be about 25degrees or 31 degrees with respect to the longitudinal axis of theextendable concertina structure 3362 when straightened.

A slit 3322 that is angled posteriorly with respect to the tube wall3352 or path 3353 (e.g. with the superior end 3326 being spaced furtherfrom the tube wall 3352 or path 3353 than the inferior end 3327) mayadvantageously be better suited to receive the strap 3310 from a lowerposition around the back of the patient's head. In an ideal set up, thestrap 3310 extends from the slit 3322 in a direction perpendicular tothe length axis 3323 of the slit 3322. Therefore, a slit 3322 that ismore posteriorly angled will better accommodate a strap 3310 that lieslow around the back of the patient's head, since it will be angled toreceive the strap 3310 from the lower angle. In contrast, a slit 3322that is oriented closer to a vertical orientation will be angled toreceive the strap 3310 from a higher position on the patient's head.Accordingly, a slit 3322 oriented at a larger angle with respect to anadjacent portion of the tube wall 3352 and/or path 3353 may provide someresistance to the strap 3310 riding up the back of the patient's head(e.g. sliding superiorly).

While other methods may be used to reduce the tendency of the strap 3310to ride up the back of the patient's head (e.g. providing a split in thestrap 3310, enabling the patient to tighten the strap 3310 and/orproviding the slit 3322 at a low position) providing the slit 3322 at aposteriorly rotated angle to the tube 3350 may provide furtherresistance to the strap 3310 riding up. In some examples, each slit 3322may be angled to receive the strap 3310 from a direction in which thestrap 3310 lies across a region of the patient's head overlaying aninferior portion of the occipital bone. In further examples, the slit3322 may be angled to receive the strap 3310 from the direction whichthe strap 3310 overlays a central or superior portion of the patient'soccipital bone.

Each slit 3322 may be oriented perpendicular to the direction from theslit of a strap anchor region against which the strap is anchored aroundthe patient's head. The strap anchor region may be a region overlayingthe patient's occipital bone, for example an inferior portion of theoccipital bone. In some examples the strap anchor region may be a regionof the patient's neck lying inferior to the patient's occipital bone. Insome examples, in some examples the strap 3310 may overlay a superiorportion of the patient's trapezius muscles or a portion of the patient'sneck or head inferior to the occipital bone and the slit 3322 may beangled to receive the strap 3310 from a corresponding direction.

For example, as shown in FIG. 8C, the slit 3322 is angled sufficientlyrearward to receive the strap 3310 from a direction in which the strap3310 lies across a posterior region of the patient's head inferior to aninferior-most portion of the patient's head. The strap 3310 may lieacross posterior surfaces of the patient's head that face in an at leastpartially inferior direction and the slit 3322 may be angledsufficiently posteriorly to receive the strap 3310 from this location.It is advantageous for the strap 3310 to lie across posterior surfacesof the patient's head that face in an at least partially inferiordirection since the eyelets are located superior to the posterior-mostportion of the strap 3310. Once tension is applied to the strap 3310,the tubes 3350 will exert a partially superior force on the strap 3310,meaning the strap 3310 may be less likely to ride up if anchored againstposterior surfaces of the patient's head that face inferiorly.

With reference to FIGS. 11A-11C, the tab 3320 comprises a superior edge3331 and an inferior edge 3332. In this example, the superior edge 3331is longer than the inferior edge 3332. The longer superior edge 3331gives the tab 3320 an asymmetrical shape pointing in more of an inferiordirection than the tab 3320 would point if the superior edge 3331 was ofan equal length to the inferior edge 3332. The slit 3322 issubstantially centred between the superior edge 3331 and an inferioredge 3332. Thus, the asymmetrical shape of the tab 3320 result in theslit 3322 being presented towards more of an inferior direction. Thisinferior pointing of the tab 3320 may advantageously reduce the tendencyof the strap 3310 from riding up the back of the patient's head.

In addition to having an oblique slit angle 3321, the slit 3322 may alsobe spaced from the tube wall 3352 by a spacing sufficient to furtherreduce a tendency of the strap 3310 to ride up the back of the patient'shead. A generous spacing between a slit or other eyelet and the tubewall 3352 advantageously may reduce the distance between the eyelet andthe back of the patient's head. A relatively short distance between theeyelet and the back of the patient's head may reduce the length of thestrap 3310 that lies laterally alongside the patient's head extendingbetween the slit 3322 and the posteriorly facing the forces of thepatient's head. This reduced distance and strap length mayadvantageously inhibit pivoting of the strap 3310 with respect to theeyelet, thereby reducing the tendency of the strap 3310 to ride upwardlyor downwardly in use.

In some examples, the inferior end 3327 of the slit 3322 may be spacedfrom the tube wall 3352 by at least 5 mm. In further examples, theinferior end 3327 of the slit 3322 may be spaced from the tube wall 3352by at least 7 mm. For example, the inferior end 3327 of the slit 3322may be spaced from the tube wall 3352 by about 8 mm, or more.

The superior end 3326 of the slit 3322 may be spaced from the tube wall3352 by at least 8 mm. In some examples, the superior end 3326 of theslit 3322 may be spaced from the tube wall 3352 by at least 10 mm. Forexample, the superior end 3326 of the slit 3322 may be spaced from thetube wall 3352 by 12 mm, or more.

In some examples, a midpoint along the slit 3322 may be spaced from thetube wall 3352 by a spacing within a range of approximately 5 mm to 30mm. A very large spacing between the eyelet and the tube wall 3352,while advantageous in increasing stability of the strap 3310, mayintroduce challenges/problems in manufacturability, weight, comfort andaesthetic appear due to the increased size of the tabs 3320. A spacingwithin the 5-30 mm range, such as with a range of 7 mm to 20 mm, mayprovide the benefits of stability to prevent the strap 3310 riding up,which avoiding or minimising issues caused by the increased size of thetabs 3320. In further examples this spacing may be within a range of 8mm to 15 mm, such as within the range of 9 mm to 13 mm. In someparticular examples the spacing may be around 9 mm to 11 mm, such asabout 9.5 mm or 9.75 mm.

5.3.2.3.3 Trough

FIG. 11C shows a close-up perspective view of one of the tabs 3320 ofthe positioning and stabilising structure 3300. As illustrated, in someexamples, the tab 3320 of the positioning and stabilising structure 3300may comprise a trough 3324 formed in the tab and located posteriorly tothe slit 3322. The trough 3324 may be formed into the body of the tab3320 in a location underneath the strap 3310. The trough 3324, in thisexample, is provided between the slit 3322 and a posterior side 3329 ofthe tab 3320. The tab 3320 may comprise an outwardly facing tab surface3328 on the side of the tab 3320 facing away from the patient (e.g. in alateral direction). The tab surface 3328 may be substantially planar inthe vicinity of the slit 3322. The trough 3324 may be formed by aportion of the tab 3320 at the trough 3324 having a lesser materialthickness than other portions of the tab 3320. The trough 3324 istherefore recessed with respect to the tab surface 3328 in this example.

The trough 3324 may have substantially the same width as the length ofthe slit 3322. That is, the trough 3324 may have a superior endproximate the superior end 3326 of the slit and may have an inferior endproximate the inferior end 3327 of the slit 3322. In this example, thetrough 3324 has substantially the same width as the strap 3310. Thetrough 3324 is configured to receive the strap 3310. The trough 3324reduces the total thickness of the strap 3310 and tab 3320. At thelocation of the trough 3324, the tab 3320 is sandwiched between twolayers of the strap 3310 (since the strap is threaded through the slitand looped back on itself). The bulk and/or thickness of the strap 3310and tab 3320 at this location may create a pressure point or point ofdiscomfort for the patient when sleeping on their side. The trough 3324may advantageously reduce the layered thickness of components at thislocation which may reduce the pressure applied to the patient's head atthis location during side sleeping.

Additionally, in this example, the trough 3324 has sides which areadjacent to sides of the strap 3310. The width of the trough 3324therefore matches the width of the strap 3310. This advantageously mayhelp keep the strap 3310 aligned and centred within the trough 3324. Itmay also provide a visual guide for the user regarding alignment of thestrap 3310.

5.3.3 Vent

In one form, the patient interface 3000 includes a vent 3400 constructedand arranged to allow for the washout of exhaled gases, e.g. carbondioxide.

In certain forms the vent 3400 is configured to allow a continuous ventflow from an interior of the plenum chamber 3200 to ambient whilst thepressure within the plenum chamber is positive with respect to ambient.The vent 3400 is configured such that the vent flow rate has a magnitudesufficient to reduce rebreathing of exhaled CO₂ by the patient whilemaintaining the therapeutic pressure in the plenum chamber in use. Thevent 3400 may provide a continuous vent flow of gas from the interior ofthe plenum chamber 3200 to ambient throughout the patient's respiratorycycle.

One form of vent 3400 in accordance with the present technologycomprises a plurality of holes, for example, about 20 to about 80 holes,or about 40 to about 60 holes, or about 45 to about 55 holes.

The vent 3400 may be located in the plenum chamber 3200. Alternatively,the vent 3400 is located in a decoupling structure, e.g., a swivel suchas elbow 3610. In the example shown in FIGS. 8A-9C, the patientinterface 3000 comprises a plurality of vents 3400. In particular, thepatient interface 3000 comprises at least one vent 3400 in the plenumchamber 3200 and at least one vent in the elbow 3610. More particularly,the plenum chamber 3200 comprises two vents 3400. Each vent 3400 on theplenum chamber 3200 comprises an array of holes. The vent 3400 on theelbow 3610 also comprises an array of holes. The vent 3400 of thepatient interface 3000 are sized and configured to provide sufficientgas washout throughout a range of therapeutic pressures.

The patient interface 3000 may comprise a diffuser configured to diffusethe flow of air though the vent to reduce vent noise and reduce jettingof air out of the vent holes. The diffuser may be provided to a coverover the vent holes. In some examples, the vent 3400 may comprise a ventmodule configured to be removed from the plenum chamber 3200. The ventmodule may comprise a diffuser.

5.3.4 Decoupling Structure(s)

In one form the patient interface 3000 includes at least one decouplingstructure, for example, a swivel or a ball and socket. For example, thepatient interface 3000 shown in FIGS. 8A-9C comprises an elbow 3610configured the swivel with respect to the positioning and stabilisingstructure 3300. In this example the elbow 3610 is configured to swivelabout an axis concentric with a circular opening in the positioning andstabilising structure 3300. In some examples of the present technology,the elbow 3610 may form part of a ball and socket joint to thepositioning and stabilising structure 3300. For example, a ring having apartially spherical inner surface may be provided to the positioning andstabilising structure 3300 and may be configured to receive the elbow3610. The elbow 3610 may have partially spherical outer surfacecomplimentary to the partially spherical inner surface of the ring,thereby enabling the elbow 3610 to swivel with respect to the ring in aplurality of axes.

5.3.5 Connection Port

Connection port 3600 allows for connection to the air circuit 4170. Inthe exemplary patient interface 3000 shown in FIGS. 8A-9C, the elbow3610 forms part of the connection port 3600. The elbow 3610, as adecoupling structure, decouples movement of the air circuit 4170 fromthe positioning and stabilising structure 3300 in order to reduce tubedrag on the positioning and stabilising structure 3300.

5.3.6 Forehead Support

In one form, the patient interface 3000 includes a forehead support3700. In other forms, the patient interface 3000 does not include aforehead support. Advantageously, the exemplary patient interface 3000shown in FIGS. 8A-9C comprises a positioning and stabilising structure3300 that is able to hold the seal-forming structure 3100 in sealingposition without connection to a forehead support or any frame or strapmembers that lie in front of the patient's face at eye level.

5.3.7 Anti-Asphyxia Valve

In one form, the patient interface 3000 includes an anti-asphyxia valve.In some examples, the patient interface 3000 includes a plurality ofanti-asphyxia valves. For example, where airflow is provided to aseal-forming structure 3100 via two fluid connections, two anti-asphyxiavalves may be provided to the patient interface 3000, one at each fluidconnection to the seal-forming structure 3100.

5.3.8 Ports

In one form of the present technology, a patient interface 3000 includesone or more ports that allow access to the volume within the plenumchamber 3200. In one form this allows a clinician to supply supplementaloxygen. In one form, this allows for the direct measurement of aproperty of gases within the plenum chamber 3200, such as the pressure.

5.4 RPT Device

An RPT device 4000 in accordance with one aspect of the presenttechnology comprises mechanical, pneumatic, and/or electrical componentsand is configured to execute one or more algorithms 4300, such as any ofthe methods, in whole or in part, described herein. The RPT device 4000may be configured to generate a flow of air for delivery to a patient'sairways, such as to treat one or more of the respiratory conditionsdescribed elsewhere in the present document.

In one form, the RPT device 4000 is constructed and arranged to becapable of delivering a flow of air in a range of −20 L/min to +150L/min while maintaining a positive pressure of at least 6 cmH₂O, or atleast 10cmH₂O, or at least 20 cmH₂O.

The RPT device may have an external housing 4010, formed in two parts,an upper portion 4012 and a lower portion 4014. Furthermore, theexternal housing 4010 may include one or more panel(s) 4015. The RPTdevice 4000 comprises a chassis 4016 that supports one or more internalcomponents of the RPT device 4000. The RPT device 4000 may include ahandle 4018.

The pneumatic path of the RPT device 4000 may comprise one or more airpath items, e.g., an inlet air filter 4112, an inlet muffler 4122, apressure generator 4140 capable of supplying air at positive pressure(e.g., a blower 4142), an outlet muffler 4124 and one or moretransducers 4270, such as pressure sensors and flow rate sensors.

One or more of the air path items may be located within a removableunitary structure which will be referred to as a pneumatic block 4020.The pneumatic block 4020 may be located within the external housing4010. In one form a pneumatic block 4020 is supported by, or formed aspart of the chassis 4016.

The RPT device 4000 may have an electrical power supply 4210, one ormore input devices 4220, a central controller, a therapy devicecontroller, a pressure generator 4140, one or more protection circuits,memory, transducers 4270, data communication interface and one or moreoutput devices. Electrical components 4200 may be mounted on a singlePrinted Circuit Board Assembly (PCBA) 4202. In an alternative form, theRPT device 4000 may include more than one PCBA 4202.

5.4.1 RPT Device Mechanical & Pneumatic Components

An RPT device may comprise one or more of the following components,including pneumatic components 4100, in an integral unit. In analternative form, one or more of the following components may be locatedas respective separate units.

5.4.1.1 Air Filter(s)

An RPT device in accordance with one form of the present technology mayinclude an air filter 4110, or a plurality of air filters 4110.

In one form, an inlet air filter 4112 is located at the beginning of thepneumatic path upstream of a pressure generator 4140.

In one form, an outlet air filter 4114, for example an antibacterialfilter, is located between an outlet of the pneumatic block 4020 and apatient interface 3000.

5.4.1.2 Muffler(s)

An RPT device in accordance with one form of the present technology mayinclude a muffler 4120, or a plurality of mufflers 4120.

In one form of the present technology, an inlet muffler 4122 is locatedin the pneumatic path upstream of a pressure generator 4140.

In one form of the present technology, an outlet muffler 4124 is locatedin the pneumatic path between the pressure generator 4140 and a patientinterface 3000.

5.4.1.3 Pressure Generator

In one form of the present technology, a pressure generator 4140 forproducing a flow, or a supply, of air at positive pressure is acontrollable blower 4142. For example the blower 4142 may include abrushless DC motor 4144 with one or more impellers. The impellers may belocated in a volute. The blower may be capable of delivering a supply ofair, for example at a rate of up to about 120 litres/minute, at apositive pressure in a range from about 4 cmH₂O to about 20 cmH₂O, or inother forms up to about 30 cmH₂O. The blower may be as described in anyone of the following patents or patent applications the contents ofwhich are incorporated herein by reference in their entirety: U.S. Pat.Nos. 7,866,944; 8,638,014; 8,636,479; and PCT Patent ApplicationPublication No. WO 2013/020167.

The pressure generator 4140 is under the control of the therapy devicecontroller 4240.

In other forms, a pressure generator 4140 may be a piston-driven pump, apressure regulator connected to a high pressure source (e.g. compressedair reservoir), or a bellows.

5.4.1.4 Anti-Spill Back Valve

In one form of the present technology, an anti-spill back valve 4160 islocated between the humidifier 5000 and the pneumatic block 4020. Theanti-spill back valve is constructed and arranged to reduce the riskthat water will flow upstream from the humidifier 5000, for example tothe motor 4144.

5.4.2 RPT Device Algorithms

As mentioned above, in some forms of the present technology, the centralcontroller may be configured to implement one or more algorithmsexpressed as computer programs stored in a non-transitory computerreadable storage medium, such as memory. The algorithms are generallygrouped into groups referred to as modules.

5.5 Air Circuit

An air circuit 4170 in accordance with an aspect of the presenttechnology is a conduit or a tube constructed and arranged to allow, inuse, a flow of air to travel between two components such as RPT device4000 and the patient interface 3000.

In particular, the air circuit 4170 may be in fluid connection with theoutlet of the pneumatic block 4020 and the patient interface. The aircircuit may be referred to as an air delivery tube. In some cases theremay be separate limbs of the circuit for inhalation and exhalation. Inother cases a single limb is used.

In some forms, the air circuit 4170 may comprise one or more heatingelements configured to heat air in the air circuit, for example tomaintain or raise the temperature of the air. The heating element may bein a form of a heated wire circuit, and may comprise one or moretransducers, such as temperature sensors. In one form, the heated wirecircuit may be helically wound around the axis of the air circuit 4170.The heating element may be in communication with a controller such as acentral controller. One example of an air circuit 4170 comprising aheated wire circuit is described in U.S. Pat. No. 8,733,349, which isincorporated herewithin in its entirety by reference.

5.5.1 Oxygen Delivery

In one form of the present technology, supplemental oxygen 4180 isdelivered to one or more points in the pneumatic path, such as upstreamof the pneumatic block 4020, to the air circuit 4170 and/or to thepatient interface 3000.

5.6 Humidifier 5.6.1 Humidifier Overview

In one form of the present technology there is provided a humidifier5000 (e.g. as shown in FIG. 5A) to change the absolute humidity of airor gas for delivery to a patient relative to ambient air. Typically, thehumidifier 5000 is used to increase the absolute humidity and increasethe temperature of the flow of air (relative to ambient air) beforedelivery to the patient's airways.

The humidifier 5000 may comprise a humidifier reservoir 5110, ahumidifier inlet 5002 to receive a flow of air, and a humidifier outlet5004 to deliver a humidified flow of air. In some forms, as shown inFIG. 5A and FIG. 5B, an inlet and an outlet of the humidifier reservoir5110 may be the humidifier inlet 5002 and the humidifier outlet 5004respectively. The humidifier 5000 may further comprise a humidifier base5006, which may be adapted to receive the humidifier reservoir 5110 andcomprise a heating element 5240.

5.6.1.1 Conductive Portion

According to one arrangement, the reservoir 5110 comprises a conductiveportion 5120 configured to allow efficient transfer of heat from theheating element 5240 to the volume of liquid in the reservoir 5110. Inone form, the conductive portion 5120 may be arranged as a plate,although other shapes may also be suitable. All or a part of theconductive portion 5120 may be made of a thermally conductive materialsuch as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm,2.5 mm or 3 mm), another heat conducting metal or some plastics. In somecases, suitable heat conductivity may be achieved with less conductivematerials of suitable geometry.

5.6.1.2 Humidifier Reservoir Dock

In one form, the humidifier 5000 may comprise a humidifier reservoirdock 5130 (as shown in FIG. 5B) configured to receive the humidifierreservoir 5110. In some arrangements, the humidifier reservoir dock 5130may comprise a locking feature such as a locking lever 5135 configuredto retain the reservoir 5110 in the humidifier reservoir dock 5130.

5.6.1.3 Water Level Indicator

The humidifier reservoir 5110 may comprise a water level indicator 5150as shown in FIG. 5A-5B. In some forms, the water level indicator 5150may provide one or more indications to a user such as the patient 1000or a care giver regarding a quantity of the volume of water in thehumidifier reservoir 5110. The one or more indications provided by thewater level indicator 5150 may include an indication of a maximum,predetermined volume of water, any portions thereof, such as 25%, 50% or75% or volumes such as 200 ml, 300 ml or 400 ml.

5.7 Glossary

For the purposes of the present technology disclosure, in certain formsof the present technology, one or more of the following definitions mayapply. In other forms of the present technology, alternative definitionsmay apply.

5.7.1 General

Air: In certain forms of the present technology, air may be taken tomean atmospheric air, and in other forms of the present technology airmay be taken to mean some other combination of breathable gases, e.g.atmospheric air enriched with oxygen.

Ambient: In certain forms of the present technology, the term ambientwill be taken to mean (i) external of the treatment system or patient,and (ii) immediately surrounding the treatment system or patient.

For example, ambient humidity with respect to a humidifier may be thehumidity of air immediately surrounding the humidifier, e.g. thehumidity in the room where a patient is sleeping. Such ambient humiditymay be different to the humidity outside the room where a patient issleeping.

In another example, ambient pressure may be the pressure immediatelysurrounding or external to the body.

In certain forms, ambient (e.g., acoustic) noise may be considered to bethe background noise level in the room where a patient is located, otherthan for example, noise generated by an RPT device or emanating from amask or patient interface. Ambient noise may be generated by sourcesoutside the room.

Automatic Positive Airway Pressure (APAP) therapy: CPAP therapy in whichthe treatment pressure is automatically adjustable, e.g. from breath tobreath, between minimum and maximum limits, depending on the presence orabsence of indications of SDB events.

Continuous Positive Airway Pressure (CPAP) therapy: Respiratory pressuretherapy in which the treatment pressure is approximately constantthrough a respiratory cycle of a patient. In some forms, the pressure atthe entrance to the airways will be slightly higher during exhalation,and slightly lower during inhalation. In some forms, the pressure willvary between different respiratory cycles of the patient, for example,being increased in response to detection of indications of partial upperairway obstruction, and decreased in the absence of indications ofpartial upper airway obstruction.

Flow rate: The volume (or mass) of air delivered per unit time. Flowrate may refer to an instantaneous quantity. In some cases, a referenceto flow rate will be a reference to a scalar quantity, namely a quantityhaving magnitude only. In other cases, a reference to flow rate will bea reference to a vector quantity, namely a quantity having bothmagnitude and direction. Flow rate may be given the symbol Q. ‘Flowrate’ is sometimes shortened to simply ‘flow’ or ‘airflow’.

In the example of patient respiration, a flow rate may be nominallypositive for the inspiratory portion of a breathing cycle of a patient,and hence negative for the expiratory portion of the breathing cycle ofa patient. Total flow rate, Qt, is the flow rate of air leaving the RPTdevice. Vent flow rate, Qv, is the flow rate of air leaving a vent toallow washout of exhaled gases. Leak flow rate, Ql, is the flow rate ofleak from a patient interface system or elsewhere. Respiratory flowrate, Qr, is the flow rate of air that is received into the patient'srespiratory system.

Humidifier: The word humidifier will be taken to mean a humidifyingapparatus constructed and arranged, or configured with a physicalstructure to be capable of providing a therapeutically beneficial amountof water (H₂O) vapour to a flow of air to ameliorate a medicalrespiratory condition of a patient.

Leak: The word leak will be taken to be an unintended flow of air. Inone example, leak may occur as the result of an incomplete seal betweena mask and a patient's face. In another example leak may occur in aswivel elbow to the ambient.

Noise, conducted (acoustic): Conducted noise in the present documentrefers to noise which is carried to the patient by the pneumatic path,such as the air circuit and the patient interface as well as the airtherein. In one form, conducted noise may be quantified by measuringsound pressure levels at the end of an air circuit.

Noise, radiated (acoustic): Radiated noise in the present documentrefers to noise which is carried to the patient by the ambient air. Inone form, radiated noise may be quantified by measuring soundpower/pressure levels of the object in question according to ISO 3744.

Noise, vent (acoustic): Vent noise in the present document refers tonoise which is generated by the flow of air through any vents such asvent holes of the patient interface.

Patient: A person, whether or not they are suffering from a respiratorycondition.

Pressure: Force per unit area. Pressure may be expressed in a range ofunits, including cmH₂O, g-f/cm² and hectopascal. 1 cmH₂O is equal to 1g-f/cm² and is approximately 0.98 hectopascal. In this specification,unless otherwise stated, pressure is given in units of cmH₂O.

The pressure in the patient interface is given the symbol Pm, while thetreatment pressure, which represents a target value to be achieved bythe mask pressure Pm at the current instant of time, is given the symbolPt.

Respiratory Pressure Therapy (RPT): The application of a supply of airto an entrance to the airways at a treatment pressure that is typicallypositive with respect to atmosphere.

Ventilator: A mechanical device that provides pressure support to apatient to perform some or all of the work of breathing.

5.7.1.1 Materials

Silicone or Silicone Elastomer: A synthetic rubber. In thisspecification, a reference to silicone is a reference to liquid siliconerubber (LSR) or a compression moulded silicone rubber (CMSR). One formof commercially available LSR is SILASTIC (included in the range ofproducts sold under this trademark), manufactured by Dow Corning.Another manufacturer of LSR is Wacker. Unless otherwise specified to thecontrary, an exemplary form of LSR has a Shore A (or Type A) indentationhardness in the range of about 35 to about 45 as measured using ASTMD2240.

Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate.

5.7.1.2 Mechanical Properties

Resilience: Ability of a material to absorb energy when deformedelastically and to release the energy upon unloading.

Resilient: Will release substantially all of the energy when unloaded.Includes e.g. certain silicones, and thermoplastic elastomers.

Hardness: The ability of a material per se to resist deformation (e.g.described by a Young's Modulus, or an indentation hardness scalemeasured on a standardised sample size).

-   -   ‘Soft’ materials may include silicone or thermo-plastic        elastomer (TPE), and may, e.g. readily deform under finger        pressure.    -   ‘Hard’ materials may include polycarbonate, polypropylene, steel        or aluminium, and may not e.g. readily deform under finger        pressure.

Stiffness (or rigidity) of a structure or component: The ability of thestructure or component to resist deformation in response to an appliedload. The load may be a force or a moment, e.g. compression, tension,bending or torsion. The structure or component may offer differentresistances in different directions.

Floppy structure or component: A structure or component that will changeshape, e.g. bend, when caused to support its own weight, within arelatively short period of time such as 1 second.

Rigid structure or component: A structure or component that will notsubstantially change shape when subject to the loads typicallyencountered in use. An example of such a use may be setting up andmaintaining a patient interface in sealing relationship with an entranceto a patient's airways, e.g. at a load of approximately 20 to 30 cmH₂Opressure.

As an example, an I-beam may comprise a different bending stiffness(resistance to a bending load) in a first direction in comparison to asecond, orthogonal direction. In another example, a structure orcomponent may be floppy in a first direction and rigid in a seconddirection.

5.7.2 Respiratory Cycle

Apnea: According to some definitions, an apnea is said to have occurredwhen flow falls below a predetermined threshold for a duration, e.g. 10seconds. An obstructive apnea will be said to have occurred when,despite patient effort, some obstruction of the airway does not allowair to flow. A central apnea will be said to have occurred when an apneais detected that is due to a reduction in breathing effort, or theabsence of breathing effort, despite the airway being patent. A mixedapnea occurs when a reduction or absence of breathing effort coincideswith an obstructed airway.

5.7.3 Anatomy 5.7.3.1 Anatomy of the Face

Ala: the external outer wall or “wing” of each nostril (plural: alar)

Alare: The most lateral point on the nasal ala.

Alar curvature (or alar crest) point: The most posterior point in thecurved base line of each ala, found in the crease formed by the union ofthe ala with the cheek.

Auricle: The whole external visible part of the ear.

(nose) Bony framework: The bony framework of the nose comprises thenasal bones, the frontal process of the maxillae and the nasal part ofthe frontal bone.

(nose) Cartilaginous framework: The cartilaginous framework of the nosecomprises the septal, lateral, major and minor cartilages.

Columella: the strip of skin that separates the nares and which runsfrom the pronasale to the upper lip.

Columella angle: The angle between the line drawn through the midpointof the nostril aperture and a line drawn perpendicular to the Frankforthorizontal while intersecting subnasale.

Frankfort horizontal plane: A line extending from the most inferiorpoint of the orbital margin to the left tragion. The tragion is thedeepest point in the notch superior to the tragus of the auricle.

Glabella: Located on the soft tissue, the most prominent point in themidsagittal plane of the forehead.

Lateral nasal cartilage: A generally triangular plate of cartilage. Itssuperior margin is attached to the nasal bone and frontal process of themaxilla, and its inferior margin is connected to the greater alarcartilage.

Greater alar cartilage: A plate of cartilage lying below the lateralnasal cartilage. It is curved around the anterior part of the naris. Itsposterior end is connected to the frontal process of the maxilla by atough fibrous membrane containing three or four minor cartilages of theala.

Nares (Nostrils): Approximately ellipsoidal apertures forming theentrance to the nasal cavity. The singular form of nares is naris(nostril). The nares are separated by the nasal septum.

Naso-labial sulcus or Naso-labial fold: The skin fold or groove thatruns from each side of the nose to the corners of the mouth, separatingthe cheeks from the upper lip.

Naso-labial angle: The angle between the columella and the upper lip,while intersecting subnasale.

Otobasion inferior: The lowest point of attachment of the auricle to theskin of the face.

Otobasion superior: The highest point of attachment of the auricle tothe skin of the face.

Pronasale: the most protruded point or tip of the nose, which can beidentified in lateral view of the rest of the portion of the head.

Philtrum: the midline groove that runs from lower border of the nasalseptum to the top of the lip in the upper lip region.

Pogonion: Located on the soft tissue, the most anterior midpoint of thechin.

Ridge (nasal): The nasal ridge is the midline prominence of the nose,extending from the Sellion to the Pronasale.

Sagittal plane: A vertical plane that passes from anterior (front) toposterior (rear). The midsagittal plane is a sagittal plane that dividesthe body into right and left halves.

Sellion: Located on the soft tissue, the most concave point overlyingthe area of the frontonasal suture.

Septal cartilage (nasal): The nasal septal cartilage forms part of theseptum and divides the front part of the nasal cavity.

Subalare: The point at the lower margin of the alar base, where the alarbase joins with the skin of the superior (upper) lip.

Subnasal point: Located on the soft tissue, the point at which thecolumella merges with the upper lip in the midsagittal plane.

Supramenton: The point of greatest concavity in the midline of the lowerlip between labrale inferius and soft tissue pogonion

5.7.3.2 Anatomy of the Skull

Frontal bone: The frontal bone includes a large vertical portion, thesquama frontalis, corresponding to the region known as the forehead.

Mandible: The mandible forms the lower jaw. The mental protuberance isthe bony protuberance of the jaw that forms the chin.

Maxilla: The maxilla forms the upper jaw and is located above themandible and below the orbits. The frontal process of the maxillaprojects upwards by the side of the nose, and forms part of its lateralboundary.

Nasal bones: The nasal bones are two small oblong bones, varying in sizeand form in different individuals; they are placed side by side at themiddle and upper part of the face, and form, by their junction, the“bridge” of the nose.

Nasion: The intersection of the frontal bone and the two nasal bones, adepressed area directly between the eyes and superior to the bridge ofthe nose.

Occipital bone: The occipital bone is situated at the back and lowerpart of the cranium. It includes an oval aperture, the foramen magnum,through which the cranial cavity communicates with the vertebral canal.The curved plate behind the foramen magnum is the squama occipitalis.

Orbit: The bony cavity in the skull to contain the eyeball.

Parietal bones: The parietal bones are the bones that, when joinedtogether, form the roof and sides of the cranium.

Temporal bones: The temporal bones are situated on the bases and sidesof the skull, and support that part of the face known as the temple.

Zygomatic bones: The face includes two zygomatic bones, located in theupper and lateral parts of the face and forming the prominence of thecheek.

5.7.3.3 Anatomy of the Respiratory System

Diaphragm: A sheet of muscle that extends across the bottom of the ribcage. The diaphragm separates the thoracic cavity, containing the heart,lungs and ribs, from the abdominal cavity. As the diaphragm contractsthe volume of the thoracic cavity increases and air is drawn into thelungs.

Larynx: The larynx, or voice box houses the vocal folds and connects theinferior part of the pharynx (hypopharynx) with the trachea.

Lungs: The organs of respiration in humans. The conducting zone of thelungs contains the trachea, the bronchi, the bronchioles, and theterminal bronchioles. The respiratory zone contains the respiratorybronchioles, the alveolar ducts, and the alveoli.

Nasal cavity: The nasal cavity (or nasal fossa) is a large air filledspace above and behind the nose in the middle of the face. The nasalcavity is divided in two by a vertical fin called the nasal septum. Onthe sides of the nasal cavity are three horizontal outgrowths callednasal conchae (singular “concha”) or turbinates. To the front of thenasal cavity is the nose, while the back blends, via the choanae, intothe nasopharynx.

Pharynx: The part of the throat situated immediately inferior to (below)the nasal cavity, and superior to the oesophagus and larynx. The pharynxis conventionally divided into three sections: the nasopharynx(epipharynx) (the nasal part of the pharynx), the oropharynx(mesopharynx) (the oral part of the pharynx), and the laryngopharynx(hypopharynx).

5.7.4 Patient Interface

Anti-asphyxia valve (AAV): The component or sub-assembly of a masksystem that, by opening to atmosphere in a failsafe manner, reduces therisk of excessive CO₂ rebreathing by a patient.

Elbow: An elbow is an example of a structure that directs an axis offlow of air travelling therethrough to change direction through anangle. In one form, the angle may be approximately 90 degrees. Inanother form, the angle may be more, or less than 90 degrees. The elbowmay have an approximately circular cross-section. In another form theelbow may have an oval or a rectangular cross-section. In certain formsan elbow may be rotatable with respect to a mating component, e.g. about360 degrees. In certain forms an elbow may be removable from a matingcomponent, e.g. via a snap connection. In certain forms, an elbow may beassembled to a mating component via a one-time snap during manufacture,but not removable by a patient.

Frame: Frame will be taken to mean a mask structure that bears the loadof tension between two or more points of connection with a headgear. Amask frame may be a non-airtight load bearing structure in the mask.However, some forms of mask frame may also be air-tight.

Headgear: Headgear will be taken to mean a form of positioning andstabilizing structure designed for use on a head. For example theheadgear may comprise a collection of one or more struts, ties andstiffeners configured to locate and retain a patient interface inposition on a patient's face for delivery of respiratory therapy. Someties are formed of a soft, flexible, elastic material such as alaminated composite of foam and fabric.

Membrane: Membrane will be taken to mean a typically thin element thathas, preferably, substantially no resistance to bending, but hasresistance to being stretched.

Plenum chamber: a mask plenum chamber will be taken to mean a portion ofa patient interface having walls at least partially enclosing a volumeof space, the volume having air therein pressurised above atmosphericpressure in use. A shell may form part of the walls of a mask plenumchamber.

Seal: May be a noun form (“a seal”) which refers to a structure, or averb form (“to seal”) which refers to the effect. Two elements may beconstructed and/or arranged to ‘seal’ or to effect ‘sealing’therebetween without requiring a separate ‘seal’ element per se.

Shell: A shell will be taken to mean a curved, relatively thin structurehaving bending, tensile and compressive stiffness. For example, a curvedstructural wall of a mask may be a shell. In some forms, a shell may befaceted. In some forms a shell may be airtight. In some forms a shellmay not be airtight.

Stiffener: A stiffener will be taken to mean a structural componentdesigned to increase the bending resistance of another component in atleast one direction.

Strut: A strut will be taken to be a structural component designed toincrease the compression resistance of another component in at least onedirection.

Swivel (noun): A subassembly of components configured to rotate about acommon axis, preferably independently, preferably under low torque. Inone form, the swivel may be constructed to rotate through an angle of atleast 360 degrees. In another form, the swivel may be constructed torotate through an angle less than 360 degrees. When used in the contextof an air delivery conduit, the sub-assembly of components preferablycomprises a matched pair of cylindrical conduits. There may be little orno leak flow of air from the swivel in use.

Tie (noun): A structure designed to resist tension.

Vent: (noun): A structure that allows a flow of air from an interior ofthe mask, or conduit, to ambient air for clinically effective washout ofexhaled gases. For example, a clinically effective washout may involve aflow rate of about 10 litres per minute to about 100 litres per minute,depending on the mask design and treatment pressure.

5.7.5 Shape of Structures

Products in accordance with the present technology may comprise one ormore three-dimensional mechanical structures, for example a mask cushionor an impeller. The three-dimensional structures may be bounded bytwo-dimensional surfaces. These surfaces may be distinguished using alabel to describe an associated surface orientation, location, function,or some other characteristic. For example a structure may comprise oneor more of an anterior surface, a posterior surface, an interior surfaceand an exterior surface. In another example, a seal-forming structuremay comprise a face-contacting (e.g. outer) surface, and a separatenon-face-contacting (e.g. underside or inner) surface. In anotherexample, a structure may comprise a first surface and a second surface.

To facilitate describing the shape of the three-dimensional structuresand the surfaces, we first consider a cross-section through a surface ofthe structure at a point, p. See FIG. 3B to FIG. 3F, which illustrateexamples of cross-sections at point p on a surface, and the resultingplane curves. FIGS. 3B to 3F also illustrate an outward normal vector atp. The outward normal vector at p points away from the surface. In someexamples we describe the surface from the point of view of an imaginarysmall person standing upright on the surface.

5.7.5.1 Curvature in One Dimension

The curvature of a plane curve at p may be described as having a sign(e.g. positive, negative) and a magnitude (e.g. 1/radius of a circlethat just touches the curve at p).

Positive curvature: If the curve at p turns towards the outward normal,the curvature at that point will be taken to be positive (if theimaginary small person leaves the point p they must walk uphill). SeeFIG. 3B (relatively large positive curvature compared to FIG. 3C) andFIG. 3C (relatively small positive curvature compared to FIG. 3B). Suchcurves are often referred to as concave.

Zero curvature: If the curve at p is a straight line, the curvature willbe taken to be zero (if the imaginary small person leaves the point p,they can walk on a level, neither up nor down). See FIG. 3D.

Negative curvature: If the curve at p turns away from the outwardnormal, the curvature in that direction at that point will be taken tobe negative (if the imaginary small person leaves the point p they mustwalk downhill). See FIG. 3E (relatively small negative curvaturecompared to FIG. 3F) and FIG. 3F (relatively large negative curvaturecompared to FIG. 3E). Such curves are often referred to as convex.

5.7.5.2 Curvature of Two Dimensional Surfaces

A description of the shape at a given point on a two-dimensional surfacein accordance with the present technology may include multiple normalcross-sections. The multiple cross-sections may cut the surface in aplane that includes the outward normal (a “normal plane”), and eachcross-section may be taken in a different direction. Each cross-sectionresults in a plane curve with a corresponding curvature. The differentcurvatures at that point may have the same sign, or a different sign.Each of the curvatures at that point has a magnitude, e.g. relativelysmall. The plane curves in FIGS. 3B to 3F could be examples of suchmultiple cross-sections at a particular point.

Principal curvatures and directions: The directions of the normal planeswhere the curvature of the curve takes its maximum and minimum valuesare called the principal directions. In the examples of FIG. 3B to FIG.3F, the maximum curvature occurs in FIG. 3B, and the minimum occurs inFIG. 3F, hence FIG. 3B and FIG. 3F are cross sections in the principaldirections. The principal curvatures at p are the curvatures in theprincipal directions.

Region of a surface: A connected set of points on a surface. The set ofpoints in a region may have similar characteristics, e.g. curvatures orsigns.

Saddle region: A region where at each point, the principal curvatureshave opposite signs, that is, one is positive, and the other is negative(depending on the direction to which the imaginary person turns, theymay walk uphill or downhill).

Dome region: A region where at each point the principal curvatures havethe same sign, e.g. both positive (a “concave dome”) or both negative (a“convex dome”).

Cylindrical region: A region where one principal curvature is zero (or,for example, zero within manufacturing tolerances) and the otherprincipal curvature is non-zero.

Planar region: A region of a surface where both of the principalcurvatures are zero (or, for example, zero within manufacturingtolerances).

Edge of a surface: A boundary or limit of a surface or region.

Path: In certain forms of the present technology, ‘path’ will be takento mean a path in the mathematical—topological sense, e.g. a continuousspace curve from f(0) to f(1) on a surface. In certain forms of thepresent technology, a ‘path’ may be described as a route or course,including e.g. a set of points on a surface. (The path for the imaginaryperson is where they walk on the surface, and is analogous to a gardenpath).

Path length: In certain forms of the present technology, ‘path length’will be taken to mean the distance along the surface from f(0) to f(1),that is, the distance along the path on the surface. There may be morethan one path between two points on a surface and such paths may havedifferent path lengths. (The path length for the imaginary person wouldbe the distance they have to walk on the surface along the path).

Straight-line distance: The straight-line distance is the distancebetween two points on a surface, but without regard to the surface. Onplanar regions, there would be a path on the surface having the samepath length as the straight-line distance between two points on thesurface. On non-planar surfaces, there may be no paths having the samepath length as the straight-line distance between two points. (For theimaginary person, the straight-line distance would correspond to thedistance ‘as the crow flies’.)

5.7.5.3 Space Curves

Space curves: Unlike a plane curve, a space curve does not necessarilylie in any particular plane. A space curve may be closed, that is,having no endpoints. A space curve may be considered to be aone-dimensional piece of three-dimensional space. An imaginary personwalking on a strand of the DNA helix walks along a space curve. Atypical human left ear comprises a helix, which is a left-hand helix,see FIG. 3Q. A typical human right ear comprises a helix, which is aright-hand helix, see FIG. 3R. FIG. 3S shows a right-hand helix. Theedge of a structure, e.g. the edge of a membrane or impeller, may followa space curve. In general, a space curve may be described by a curvatureand a torsion at each point on the space curve. Torsion is a measure ofhow the curve turns out of a plane. Torsion has a sign and a magnitude.The torsion at a point on a space curve may be characterised withreference to the tangent, normal and binormal vectors at that point.

Tangent unit vector (or unit tangent vector): For each point on a curve,a vector at the point specifies a direction from that point, as well asa magnitude. A tangent unit vector is a unit vector pointing in the samedirection as the curve at that point. If an imaginary person were flyingalong the curve and fell off her vehicle at a particular point, thedirection of the tangent vector is the direction she would betravelling.

Unit normal vector: As the imaginary person moves along the curve, thistangent vector itself changes. The unit vector pointing in the samedirection that the tangent vector is changing is called the unitprincipal normal vector. It is perpendicular to the tangent vector.

Binormal unit vector: The binormal unit vector is perpendicular to boththe tangent vector and the principal normal vector. Its direction may bedetermined by a right-hand rule (see e.g. FIG. 3P), or alternatively bya left-hand rule (FIG. 3O).

Osculating plane: The plane containing the unit tangent vector and theunit principal normal vector. See FIGS. 3O and 3P.

Torsion of a space curve: The torsion at a point of a space curve is themagnitude of the rate of change of the binormal unit vector at thatpoint. It measures how much the curve deviates from the osculatingplane. A space curve which lies in a plane has zero torsion. A spacecurve which deviates a relatively small amount from the osculating planewill have a relatively small magnitude of torsion (e.g. a gently slopinghelical path). A space curve which deviates a relatively large amountfrom the osculating plane will have a relatively large magnitude oftorsion (e.g. a steeply sloping helical path). With reference to FIG.3S, since T2>T1, the magnitude of the torsion near the top coils of thehelix of FIG. 3S is greater than the magnitude of the torsion of thebottom coils of the helix of FIG. 3S

With reference to the right-hand rule of FIG. 3P, a space curve turningtowards the direction of the right-hand binormal may be considered ashaving a right-hand positive torsion (e.g. a right-hand helix as shownin FIG. 3S). A space curve turning away from the direction of theright-hand binormal may be considered as having a right-hand negativetorsion (e.g. a left-hand helix).

Equivalently, and with reference to a left-hand rule (see FIG. 3O), aspace curve turning towards the direction of the left-hand binormal maybe considered as having a left-hand positive torsion (e.g. a left-handhelix). Hence left-hand positive is equivalent to right-hand negative.See FIG. 3T.

5.7.5.4 Holes

A surface may have a one-dimensional hole, e.g. a hole bounded by aplane curve or by a space curve. Thin structures (e.g. a membrane) witha hole, may be described as having a one-dimensional hole. See forexample the one dimensional hole in the surface of structure shown inFIG. 3I, bounded by a plane curve.

A structure may have a two-dimensional hole, e.g. a hole bounded by asurface. For example, an inflatable tyre has a two dimensional holebounded by the interior surface of the tyre. In another example, abladder with a cavity for air or gel could have a two-dimensional hole.See for example the cushion of FIG. 3L and the example cross-sectionstherethrough in FIG. 3M and FIG. 3N, with the interior surface boundinga two dimensional hole indicated. In a yet another example, a conduitmay comprise a one-dimension hole (e.g. at its entrance or at its exit),and a two-dimension hole bounded by the inside surface of the conduit.See also the two dimensional hole through the structure shown in FIG.3K, bounded by a surface as shown.

5.8 Other Remarks

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being used to construct acomponent, obvious alternative materials with similar properties may beused as a substitute. Furthermore, unless specified to the contrary, anyand all components herein described are understood to be capable ofbeing manufactured and, as such, may be manufactured together orseparately.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated herein by referencein their entirety to disclose and describe the methods and/or materialswhich are the subject of those publications. The publications discussedherein are provided solely for their disclosure prior to the filing dateof the present application. Nothing herein is to be construed as anadmission that the present technology is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dates,which may need to be independently confirmed.

The terms “comprises” and “comprising” should be interpreted asreferring to elements, components, or steps in a non-exclusive manner,indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, orsteps that are not expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular examples, it is to be understood that these examples aremerely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

It is therefore to be understood that numerous modifications may be madeto the illustrative examples and that other arrangements may be devisedwithout departing from the spirit and scope of the technology.

5.9 Reference Signs List

-   1000 Patient-   1100 Bed partner-   3000 Patient interface-   3100 Sealing or seal-forming structure-   3150 cushion module-   3160 Pillows cushion module-   3165 Nasal pillow-   3200 Plenum chamber-   3300 Positioning and stabilising structure/headgear-   3301 Force from upper portions of tubes-   3302 Force from strap-   3303 Sealing force tension-   3304 Superior tube portion-   3305 First end of the superior tube portion-   3306 Second end of the superior tube portion-   3308 Point alongside tab-   3310 Strap-   3313 Split-   3320 Tab-   3321 Slit angle-   3322 Slit-   3323 Length axis of the slit-   3324 Trough-   3325 Point along tubes proximate strap-   3326 Superior end of slit-   3327 Inferior end of slit-   3328 Tab surface-   3329 Posterior side-   3331 Superior edge of tab-   3332 Inferior edge of tab-   3347 Rounded edges-   3348 Patient contacting side-   3349 Non-patient contacting side-   3350 Gas delivery tubes-   3352 Tube wall-   3353 Path-   3354 Tangent to the path-   3355 Slit-adjacent portion-   3362 Extendable concertina structure-   3363 Non-extendable tube section-   3364 Sleeve-   3370 Ridge connecting portions-   3372 Ridge-   3373 Groove-   3374 Curved ridge portion-   3375 Straight ridge portion-   3376 Curved groove portion-   3377 Straight groove portion-   3382 Interior Ridge-   3383 Interior Groove-   3390 Fluid connection opening-   3400 Vent-   3600 Connection port-   3610 Elbow-   4000 RPT device-   4010 External housing-   4012 Upper portion-   4014 Lower Portion-   4015 Panel-   4016 Chassis-   4018 Handle-   4020 Pneumatic block-   4100 Pneumatic components-   4110 Air filter-   4112 Inlet air filter-   4114 Outlet air filter-   4122 Inlet muffler-   4124 Outlet muffler-   4140 Pressure generator-   4142 Controllable blower-   4144 Brushless DC motor-   4170 Air circuit-   4200 Electrical components-   4202 Printed Circuit Board Assembly (PCBA)-   4210 Electrical power supply-   4220 Input devices-   4270 Transducers-   5000 Humidifier-   5002 Humidifier inlet-   5004 Humidifier outlet-   5006 Humidifier base-   5110 Humidifier reservoir-   5130 Humidifier reservoir dock

1-20. (canceled)
 21. A positioning and stabilising structure for apatient interface, the positioning and stabilising structure configuredto provide a force to hold a seal-forming structure of the patientinterface in a therapeutically effective position on a patient's head,the positioning and stabilising structure comprising: one or more gasdelivery tubes to receive a flow of air from a connection port on top ofthe patient's head and to deliver the flow of air to an entrance of thepatient's airways via the seal-forming structure, each of the one ormore gas delivery tubes being constructed and arranged to contact, inuse, at least a region of the patient's head superior to an otobasionsuperior of the patient's head, each of the one or more gas deliverytubes comprising: a superior tube portion configured, in use, to overliea superior region of the patient's head, the superior tube portioncomprising: a first end configured, in use, to overlie a superiorportion of the patient's head at or proximate the sagittal plane of thepatient's head; a second end configured, in use, to overlie a sideportion of the patient's head; and one or more stiffened portionsbetween the first end and the second end configured to provide a higherresistance to relative movement between the first end and the second endin an anterior and/or posterior direction than in a superior and/orinferior direction in use; and an inferior tube portion connected to thesecond end of the superior tube portion and configured to connect to theseal-forming structure.
 22. The positioning and stabilising structure ofclaim 21, wherein the one or more gas delivery tubes comprises two gasdelivery tubes, each positioned on a respective side of the patient'shead in use.
 23. The positioning and stabilising structure of claim 22,further comprising at least one strap connected between the gas deliverytubes and configured to overlie or lie inferior to an occipital bone ofthe patient's head in use.
 24. The positioning and stabilising structureof claim 22, wherein the two gas delivery tubes are integrally formed.25. The positioning and stabilising structure of claim 21, wherein theone or more gas delivery tubes comprises a single gas delivery tubeconfigured to overlie the patient's head on one side thereof and thepositioning and stabilising structure comprises a stabilising componentprovided on the other side of the patient's head between the single gasdelivery tube and the seal-forming structure.
 26. The positioning andstabilising structure of claim 21, wherein in each of the one or moregas delivery tubes, the one or more stiffened portions comprises astiffened portion provided to an anterior side of the superior tubeportion.
 27. The positioning and stabilising structure of claim 21,wherein in each of the one or more gas delivery tubes, the one or morestiffened portions comprises a stiffened portion provided to a posteriorside of the superior tube portion.
 28. The positioning and stabilisingstructure of claim 21, wherein in each of the one or more gas deliverytubes, the superior tube portion comprises two stiffened portions. 29.The positioning and stabilising structure of claim 28, wherein in eachof the one or more gas delivery tubes, the superior tube portioncomprises a stiffened portion provided to an anterior side of thesuperior tube portion and a stiffened portion provided to a posteriorside of the superior tube portion.
 30. The positioning and stabilisingstructure of claim 21, wherein in each of the one of more gas deliverytubes, the second end of the superior tube portion is positionedlaterally and inferiorly of the first end of the superior tube portion,in use.
 31. The positioning and stabilising structure of claim 21,wherein in each of the one or more gas delivery tubes, the superior tubeportion comprises a cross section comprising long sides and short sides,one of the long sides being configured to lie against the patient'shead.
 32. The positioning and stabilising structure of claim 31, whereinthe cross section comprises corners between the long sides and the shortsides that are rounded, or the short sides are rounded.
 33. Thepositioning and stabilising structure of claim 21, wherein in each ofthe one or more gas delivery tubes, the superior tube portion comprisesan extendable portion.
 34. The patient interface of claim 33, whereinthe extendable portion comprises an extendable concertina structureformed in a tube wall of the gas delivery tube.
 35. The positioning andstabilising structure of claim 21, wherein each of the one or more gasdelivery tubes comprises a tube wall and in each of the one or more gasdelivery tubes, the superior tube portion comprises a plurality of foldsin the tube wall alternatingly forming a plurality of ridges and aplurality of grooves.
 36. The positioning and stabilising structure ofclaim 35, wherein in each of the one or more gas delivery tubes, each ofthe one or more stiffened portions comprises a plurality of connectingportions formed in the tube wall, each of the plurality of connectingportions connecting a pair of adjacent ridges.
 37. The positioning andstabilising structure of claim 21, wherein in each of the one or moregas delivery tubes, each of the one or more stiffened portions areintegrally formed with the superior tube portion.
 38. The positioningand stabilising structure of claim 21, wherein each of the one or moregas delivery tubes comprises a tube wall and in each of the one or moregas delivery tubes, each of the one or more stiffened portions isstiffened by one or more rigidising components.
 39. The positioning andstabilising structure of claim 38, wherein each rigidising componentcomprises a higher stiffness than the tube wall and is embedded withinthe tube wall.
 40. A patient interface comprising: a plenum chamberpressurisable to a therapeutic pressure of at least 6 cmH₂O aboveambient air pressure, said plenum chamber including a pair of plenumchamber inlet ports sized and structured to receive a flow of air at thetherapeutic pressure for breathing by a patient; a seal-formingstructure constructed and arranged to seal with a region of thepatient's face surrounding an entrance to the patient's airways forsealed delivery of the flow of air at the therapeutic pressurethroughout the patient's respiratory cycle in use, said seal-formingstructure having a hole therein such that the flow of air at saidtherapeutic pressure is delivered to at least an entrance to thepatient's nares, the seal-forming structure constructed and arranged tomaintain said therapeutic pressure in the plenum chamber throughout thepatient's respiratory cycle in use; the positioning and stabilisingstructure of claim 21 comprising a pair of gas delivery tubes, each ofthe gas delivery tubes being configured to be connected to acorresponding one of the plenum chamber inlet ports; and a ventstructure comprising a plurality of holes formed on the plenum chamberto allow a continuous flow of gases exhaled by the patient from aninterior of the plenum chamber to ambient, said vent structure beingsized and shaped to maintain the therapeutic pressure in the plenumchamber in use, wherein the patient interface is configured to allow thepatient to breath from ambient through their mouth in the absence of aflow of pressurised air through the plenum chamber inlet port, or thepatient interface is configured to leave the patient's mouth uncovered.